Date   

Re: SHOULD THE SCALE ILLUM. ADJUST THE TRIG HOLDOFF ON A 2246? i DONT THINK SO...

David Hall
 

Hi thanks for your input. this is Exactly how I feel about it -


(I do not see any way short of a connector going to the wrong place or being
misaligned for the scale illumination control to affect anything except the
scale illumination because that is the only thing it connects to.)


So is it plausible that my hunch is right about the PS? because it seems to be that the scale illumination circuit is drawing its load but seemingly weakening the rest of the power distribution or causing a parasitic effect in other words how could this be happening. the trigger worked before and I haven't touched or changed a thing. Or could the processor be mapping the wrong control configs i.e. sharing three different controls for one(in this case two results for one control :P) function? still that cant make sense if the scale illumination circuit is all by itself.
Bewildered.
David


Re: SHOULD THE SCALE ILLUM. ADJUST THE TRIG HOLDOFF ON A 2246? i DONT THINK SO...

 

My 2247A does this or something similar but I think I know the reason.

When changing the scale illumination, the entire CRT image including any traces
and the readout shifts by a tiny bit diagonally. I think this is caused by the
change in static magnetic field from the scale illumination circuit pushing on
the electron beam.

On Mon, 08 Sep 2014 12:43:00 -0500, you wrote:

On my 2247 the scale illumination affects the deflection factor
slightly. I haven't investigated why, but everything else works normally.


TM506 v. TM515 the rest of the story....

 

To be 100% clear, I use a lot of TM515's to set up test stations, and have 2 sets running right now, BUT they are not as good for bench use compared to the TM506 because:

1. the flipping power switch in on the back! the BACK! what the hell???? how is that good in ANY applciation?
2. the fan makes a noise like a vacuum cleaner dueling with a leaf blower.
3. no HP compartment. and why the heck not? what, nobody ever wants a power supply in the field?

4. doesn't stack well.

5. there's no good place to store the "handy" covers, which is why so many go missing in later life. virtually only 1 in 4 still has them today. what does that tell you abotu actual use?



otherwise they are great to rove with except for the incredible back-breaking weight.
for bench use, the TM506 (or if your tastes run that way) TM5006 just works better, which only makes sense, it was after all, designed to work there.


and dennis, when larry is up here this weekend, we are going to eat blueberry pancakes and bacon, with real maple syrup, and think of you while we play with TM500 stuff. down there, in the bacon-free zone.



by the way, I have't really had any special problems with the SC504 or any of the others. I run a lot of those little scopes of every type (sc501,2,3,4), and other then initially getting them broken off of ebay, have yet to have one fail except for the time I backed a rolling lab chair into the vertical knobs of a rack mounted TM506 system and smashed them to smithereens. I can't really blame the scope for that artful move.



all the best,
walter
sphere reaearch corp.


Re: in Praise of the under-appreciated TM506

 

I went to check the schematics for the DC505 and TM5006 against each other and
ran across a cryptic note I made and forgot about reminding me to check page 2-3
of the TM5006 service manual which happens to contain this warning:

"NOTE - The DC 505, DC 505A, and LA501W plug-ins are not compatible with this
power module."

Both the DC 503 and DC 505 bridge the chassis and power supply grounds through
the rear edge connector.

One big difference I see though is that the DC 503 derives its +5 volt supply
from the mainframe +11.5 volts DC supply (+8 volts DC on the TM5006 from the
switcher) while the DC 505 rectifies the output of the 18VCT AC supply to
produce the same +11.5 volts. The TM5006 limits the 18VCT AC output to 350mA
per compartment while the TM506 limits it to a total load of 6.5 amps maximum
shared which is significantly higher although it is shared between the 18VCT AC
and +11.5 DC supplies.

I do not have schematics for the LA501.

On 08 Sep 2014 08:46:18 -0700, you wrote:

Part of the TM5006/3 development project included verifying the operation of all legacy TM500 modules in the new mainframes. By design, they were all supposed to work. I believe that there is only one exception – a counter (DC505?? not sure). If my memory serves me right, its problem is not voltage, but a grounding issue. The ground distribution in the DC supplies is different in the TM5006/3 than in the TM50x mainframes.

- Steve


Windows XP

 

Rich,

I have an ISO file of Windows XP OEM with Service Pack 2 that I just copied from a Dell OEM CD with Dell logos (so I know it is virus free and I haven't modified it in any way). I have used this CD to install Windows XP in a variety of computers (not just Dell) so I know it works. I have also used it to repair several installations for friends/family. I have even been able to remove any Dell trademarks when I wanted to. I can put it in a drop box folder and share it with you if you like.

This email is direct to you because I don't want to post links and information in public. Let me know by return mail to this address if you want the link to the drop box and I will send it in a separate email.

Mac


Re: Tek 310 HV transformer

Ed Breya
 

The potting compound is probably a glass- or alumina-filled epoxy - not for strength, but for fire retardant characteristics in the event of an arc/meltdown situation. Possibly for better cooling too, if it has a lot of alumina. Ed


Re: SHOULD THE SCALE ILLUM. ADJUST THE TRIG HOLDOFF ON A 2246? i DONT THINK SO...

Cliff White
 

On my 2247 the scale illumination affects the deflection factor
slightly. I haven't investigated why, but everything else works normally.



Respectfully,
Cliff White, W5CNW
w5cnw@... <mailto:w5cnw@...>
On 09/08/2014 09:50 AM, David @DWH [TekScopes] wrote:

I do not see any way short of a connector going to the wrong place or
being
misaligned for the scale illumination control to affect anything
except the
scale illumination because that is the only thing it connects to.

The scale intensity and A intensity are adjacent on the W900 connector
(schematic 7) so maybe it is misaligned. Further, the scale intensity
is a 0 to
+15 volt signal and the A intensity signal is -2.5 to +2.5 volts. The
input
multiplexor will only handle signals from -7.5 to +5 volts; if an input is
above +5 volts, then it may "leak" although looking at the schematic I
do not
see how it would get into the holdoff control. This may depend on the
order in
which the processor reads them though.

The other controls including the intensity controls and the holdoff
control are
multiplexed both on their inputs and outputs so having them interact
with each
other is a certainly possible if something is wrong there.

On 07 Sep 2014 16:12:24 -0700, you wrote:

Hello Thanks for having me. Can anybody confirm that according to the
schematic for the 2246 the scale illumination board should not be able
to adjust the trig holdoff when I turn the knob. I'm presuming this
would indicate a powersupply issue? to add to that the readout
intensity and the A intensity also adjust the trig holdoff. "Time
signal to small" is the error. And the unit wont trigger.
Any Thoughts.
Thanks in advance.
David


[Non-text portions of this message have been removed]


Re: [OT] Windows XP?

Mike Merigliano
 

Hello, I have an OEM CD that I could convert to an ISO for you, but I think you would be stuck with lots of Dell add-ons when it installs.

But if I were you, I would buy a new disk from that big auction site; I noticed some for about $10.

On 9/7/2014 7:10 PM, 'Richard R. Pope' mechanic_2@... [TekScopes] wrote:
Mike,
I spent over two hours and I didn't find anything that I would
trust. The last thing that I want is to introduce a virus to my network
and my other systems.
Thanks,
rich!




------------------------------------

------------------------------------


------------------------------------

Yahoo Groups Links



.


Re: 370A floppy drive?

Joel
 

Craig, Good information. Is there any chance I could buy a know good floppy from you that works in your 370? At least then I know for sure the drive is good.


Thank to everyone for your suggestions too. Got to love this stuff!..


Joe


Re: Tek 310 HV transformer

Dave Wise
 

When scavenging TV flyback cores, I cut open one of the winding packs. It was made around 2000. As far as I can tell, it uses only one potting material. It is white, hard, dense, and brittle. Breaks look like ceramic, and it's extremely abrasive, taking a hacksaw blade from new to dead in one cut. The primary was probably layer-wound but I couldn't get a good look. The secondary was definitely layered and probably standard back-and-forth, with several sheets of thick, tough, stiff transparent film between each layer, and a wide margin at each end. The annular margin spaces were filled with potting material, but as far as I could tell the wire itself was not surrounded by impregnant. Strands separated and unwound easily, although only for part of a turn due to the difficulty of removing the interlayer insulation consistently.

I have made no progress on my transformer since I created the bobbin. I am busy exploring the interaction between the switching transistors and the original resonant transformer. Collector current is a damped oscillation, with several amps on the first reverse half-cycle driving the transistors deeply into inverse mode and filling the depletion region with carriers that have to be removed all over again. The appearance of this "second turn-off" creates a region where the control law goes flat or even slightly negative, with a bimodal operating point. Yet as far as I can tell, it's normal.

When I get around to winding, I will use masking tape. I have a roll of Kapton, but I'm keeping it in reserve. Like Manfred, I prefer to make do with cheap materials, going up-scale only if the smoke gets out.

Dave Wise
________________________________________
From: TekScopes@... [TekScopes@...]
Sent: Saturday, September 06, 2014 5:29 AM
To: TekScopes@...
Subject: Re: [TekScopes] Tek 310 HV transformer

[snip]

Our good buddies in the TV flyback land used a double potting
technique: First with a low loss silicone RTV rubber, and
then with a hard as nails, usually black, zero water infusion
epoxy. I had hoped that tektronix followed that same lead
with the black windings, but I haven't cut one in half yet,
so I don't know.

-Chuck Harris


Re: in Praise of the under-appreciated TM506

Ed Breya
 

As I recall, all TM500 plugs should work in the 500X mainframes, especially at lab conditions. If there are any exceptions, I think they would be listed in the mainframe manuals.

The nominal +8 and +/-26 V were chosen to be comfortably higher than the supposed worst case BOR (bottom of ripple) of a maximally loaded 500 series mainframe at lowest specified line voltage and frequency. Since most plugs used linear dropping regulators, and they were supposed to work in the original 500 mainframes at worst case conditions, then running them just above BOR should minimize their power dissipation, and that of the mainframe pass transistors. Any that used switching regulators, or the HV supplies of scopes, would likely be a little less efficient at the lower voltage, but they should work if they did in the 500 frames, and still benefit from less dissipation in the linear regulator portions.

Most of this had to be done empirically, with a large sampling of plug-ins and mainframes, analysis of the specs of all the pieces and possible and likely combinations and interactions, and delving into undefined and unspecified characteristics, while also anticipating the expected higher power needs of the concurrent 5000 series plug-in designs.

Ed


Re: in Praise of the under-appreciated TM506

 

the sc504 has reliability problems in any power supply


Jerry Massengale

-----Original Message-----
From: ditter2@... [TekScopes] <TekScopes@...>
To: TekScopes <TekScopes@...>
Sent: Mon, Sep 8, 2014 10:46 am
Subject: [TekScopes] Re: in Praise of the under-appreciated TM506






My friend Dennis,

I think you are both correct. As I read it, Walter is using the TM515 in a static bench top application. The TM506 is much better for this. In addition to the form factor issues, the TM515 lacks the high power slot needed to get full current capability from the PS503A. Even the TM504 has one.

But when you need to travel, the TM515 is great for the reasons you mention.

I want to dispel a misstated understanding earlier in this thread. It was stated that some plug-ins such as the SC504 have reliability problems when running in a TM5006/3 because the regulated +28 V is lower than the unregulated +33 V in the TM50x frames. If this is truly the case, the SC504 or other plug-ins with this problem will have more reliability issues in the TM50x under certain conditions.

Being unregulated in the linear supply versions (TM50x), the rms value of the DC supplies will change under load and line conditions. With a high plug-in load, the rms value of the +33 V will be well under +28 V when the line voltage is slightly below the center of the selected range. The DC voltages listed are typical measured with no load with the line voltage at the exact center of the selected range.

Part of the TM5006/3 development project included verifying the operation of all legacy TM500 modules in the new mainframes. By design, they were all supposed to work. I believe that there is only one exception – a counter (DC505?? not sure). If my memory serves me right, its problem is not voltage, but a grounding issue. The ground distribution in the DC supplies is different in the TM5006/3 than in the TM50x mainframes.

Ed – did I miss anything? (one of the frequent contributors to this forum designed the TM5006)

- Steve


---In TekScopes@..., <dennis@...> wrote :

Walter's experiences with the exceptional reliability of the TM5xx
mainframes is similar to mine. Their only complaint I hear from people is
about the excessive noise of the fans

I do check each new one I buy to be sure all the pass transistors and
voltages are OK and I make sure the line voltage setting on the back panel
is set properly to the mid-range of the 115V power line. Then I throw it on
top of all the others I own and it works forever.

I do disagree with Walter on one small point: The portability of the TM515
is very handy anytime you have to travel. I fill it with signal generators
and bring it with me to all the swap meets I go to. All those signals make
it easy to put interesting displays on all the scopes my friends have for
sale. The TM515 is quite rugged and well thought out. Front and rear covers
and a place to store the bail inside the cover make it a very safe way to
take a variety of instruments with you. There is room for cables inside the
front cover. The TM515 was not intended to be permanent bench instrument.

If only Walter and Susan would come to visit more often and bring me some
TM500 plugins when they come then maybe Walter would have a greater
appreciation for the TM515 :)

Dennis Tillman W7PF


Re: in Praise of the under-appreciated TM506

ditter2
 

My friend Dennis,

I think you are both correct. As I read it, Walter is using the TM515 in a static bench top application. The TM506 is much better for this. In addition to the form factor issues, the TM515 lacks the high power slot needed to get full current capability from the PS503A. Even the TM504 has one.

But when you need to travel, the TM515 is great for the reasons you mention.

I want to dispel a misstated understanding earlier in this thread. It was stated that some plug-ins such as the SC504 have reliability problems when running in a TM5006/3 because the regulated +28 V is lower than the unregulated +33 V in the TM50x frames. If this is truly the case, the SC504 or other plug-ins with this problem will have more reliability issues in the TM50x under certain conditions.

Being unregulated in the linear supply versions (TM50x), the rms value of the DC supplies will change under load and line conditions. With a high plug-in load, the rms value of the +33 V will be well under +28 V when the line voltage is slightly below the center of the selected range. The DC voltages listed are typical measured with no load with the line voltage at the exact center of the selected range.

Part of the TM5006/3 development project included verifying the operation of all legacy TM500 modules in the new mainframes. By design, they were all supposed to work. I believe that there is only one exception – a counter (DC505?? not sure). If my memory serves me right, its problem is not voltage, but a grounding issue. The ground distribution in the DC supplies is different in the TM5006/3 than in the TM50x mainframes.

Ed – did I miss anything? (one of the frequent contributors to this forum designed the TM5006)

- Steve


---In TekScopes@..., <dennis@...> wrote :

Walter's experiences with the exceptional reliability of the TM5xx
mainframes is similar to mine. Their only complaint I hear from people is
about the excessive noise of the fans

I do check each new one I buy to be sure all the pass transistors and
voltages are OK and I make sure the line voltage setting on the back panel
is set properly to the mid-range of the 115V power line. Then I throw it on
top of all the others I own and it works forever.

I do disagree with Walter on one small point: The portability of the TM515
is very handy anytime you have to travel. I fill it with signal generators
and bring it with me to all the swap meets I go to. All those signals make
it easy to put interesting displays on all the scopes my friends have for
sale. The TM515 is quite rugged and well thought out. Front and rear covers
and a place to store the bail inside the cover make it a very safe way to
take a variety of instruments with you. There is room for cables inside the
front cover. The TM515 was not intended to be permanent bench instrument.

If only Walter and Susan would come to visit more often and bring me some
TM500 plugins when they come then maybe Walter would have a greater
appreciation for the TM515 :)

Dennis Tillman W7PF


Re: [OT] Windows XP?

Richard Solomon <dickw1ksz@...>
 

Try Craigslist.

73, Dick, W1KSZ

On Mon, Sep 8, 2014 at 2:04 AM, Gordon @GordonW [TekScopes] <
TekScopes@...> wrote:





On 07/09/2014 21:19, poldhu1901@... [TekScopes] wrote:
I have not been able to find a good copy of XP Pro on the web. Also
my ID is for an OEM copy. Anybody have any other ideas?
You have checked it's not in an &#92;i386 folder on the old hard disk
haven't you? It used to be the norm to put a copy there (or &#92;W95, &#92;W98
etc going back a bit).

Gordon


Re: Tek 310 HV transformer

 

On Mon, 08 Sep 2014 14:56:44 +0000, you wrote:

David,

I like the amber Kapton tape which is used for masking printed circuit boards
during reflow and wave soldering operations. It is a little expensive but
can often be found now in electronics stores.
Not here... But sure Kapton is a good material for this.

The best self-adhesive tape for transformers that I can buy here is yellow Mylar
tape, the same kind that is used in most transformers in consumer equipment, but
even that is unreasonably expensive here, so I don't use it.
The Kapton tape for solder masking has some kind of silicon (?) adhesive which
works well at high temperature and does not dry out or leave a residue behind.
In production we used it to hold assemblies together while baking them.

I suspect this kind of tape would be overkill for a transformer but maybe that
is a good thing in this case.

There is also a cheaper bright blue tape that is more flexible but I do not
remember what it is made of.
I haven't seen that for sale, but I have seen it in commercially made
transformers. I guess it's mylar too.
It seems likely from what I remember. It was just more stretchable then I
typically associate with Mylar which may be an advantage over the Kapton tape in
transformer applications.

We got it as a less expensive replacement for the Kapton tape but I did not like
it as much.


Re: 370A floppy drive?

Craig
 

Used one of these on a daily basis for many years. It will only work with a low density floppy.

You can use the 1.44 high density floppy but you have to put a piece of opaque tape over the hole to make the 370 think it is low density.

As I rmember, the floppy has to be formatted in the 370 for it to be recognized.

Craig
--------------------------------------------


Re: tantalum capacitor color code

 

On Mon, 08 Sep 2014 10:37:55 -0400, you wrote:

At 09:34 AM 9/8/2014, edbreya wrote:

Even in real life with good lighting it's sometimes hard to discern the colors on poorly marked parts, but extra context helps to eliminate certain combinations.
That is why it is nice to have a presumed good specimen to measure.
I either look the value up in the service manual or find the same part in some
other area to measure. The color codes on dipped tantalums are just too
unreliable.

I rarely care about the voltage rating though because I usually voltage derate
the replacement part anyway based on what is inexpensively available. I have a
local electronics store which has various NOS solid tantalums but their
selection is somewhat eccentric.


Re: Tek 310 HV transformer

Manfred Mornhinweg
 

David,

I like the amber Kapton tape which is used for masking printed circuit boards
during reflow and wave soldering operations. It is a little expensive but
can often be found now in electronics stores.
Not here... But sure Kapton is a good material for this.

The best self-adhesive tape for transformers that I can buy here is yellow Mylar tape, the same kind that is used in most transformers in consumer equipment, but even that is unreasonably expensive here, so I don't use it.

There is also a cheaper bright blue tape that is more flexible but I do not
remember what it is made of.
I haven't seen that for sale, but I have seen it in commercially made transformers. I guess it's mylar too.


Ed,

I don't know if those windings were supposed to be bifilar -
In series production it makes a lot of sense to make them bifiliar. It allows saving winding time, and there is about half as much voltage between layers. As a bonus, the coupling factor (and thus the voltage tracking) is optimal.

I like your idea of putting the hot ends of the windings in the middle - that
also leaves more total stacking height to the outer layers since the cold end
will shield.
I have to see whether it works!

Another unknown is the relative phasing of the windings, which
is not shown as far as I know.
I think it _is_ shown: The phasing is simply like the orientation in the schematic. The rule in schematics is simple:

- When phasing dots are used, they tell the phasing.
- When such dots are not used, the drawing sense (which side is up, or left) tells phasing, or the phasing doesn't matter.

If anybody draws a schematic in which phasing is significant, without using phasing dots, and draws the windings connected with random phasing, he is either not very knowledgeable, or is trying to confuse the reader! I don't think that any of those two applies to Tektronix. So I think we can take the scope's schematic to imply phasing by the sense the windings are drawn.

For best regulation I would think that both HV
rectifiers would want to conduct on the power stroke, or at least on the same
stroke.
I'm quite sure that they have to be in the same phase, because the waveform isn't totally symmetrical.

the only issue is the phase to the primary,
Thanks to the parallel capacitor, the transformer resonates, with a Q of roughly 5. So the waveform approximates a sine, although a somewhat distorted one, and I think the phasing between the primary and secondary isn't highly critical. Still I'm winding my transformer with the phasing shown in the schematic.

which is easy to swap experimentally.
Only as long as you wind the plate winding separate from the feedback winding, rather than as a single winding with a "center tap" - which isn't really at the center!

Wound as shown in the schematic, changing the phase would require rewinding the transformer.

Chuck,

It is easy to combine bifilar and universal winding, I do it all the time, as
did tektronix. I just feed two wires through the same hole in the winding
stylus.
How do you keep the two wires from swapping places at random, with one mounting over the other? Does that work out by itself, or do you have to use any tricks?

many of the primaries are parallel bifilar.
I think thay did this simply so they could wind both the primary and secondaries with the same wire - a very practical setup. And the choice of #38 wire was probably a compromise: For the currents involved, it's overkill for the secondaries, and two in parallel for the primary is a little on the tight side, but workable.

Using wires of different sizes might be a problem when making a single universal-wound coil assembly.

In my transformer I'm using a single #33 for the primary, which is comfortable for the current involved, and #39 for the secondaries, simply because it's the thinnest I have on hand right now! It's still overkill.


John,

I measured the low ends on my scope and get 100V on the cathode low side and
+80 to +110 on the grid low side.
About the same here.

One thing about the bifiliar winding of the two wire at the same time is
that they are at about the same potential so you have half the turns per
layer because you have two wires. So you have about half the voltage + the
voltage difference between the two windings.
Yes. And that's quite important when you are relying just on the wire's insulation.

For just a simple layer winding I had to use two small motors on to hold the
reels of wire with a bit of back torque and a small stepper motor to turn
the coil and count turns. I use a chop stick with a double folded piece of
paper taped to it as the wire guide.
Your system is high tech compared to mine! I have an old winding machine with two speeds (SLOW, and VERY SLOW) and a turns counter. I stick the spool of wire on a screwdriver held in a vise, and guide the wire by hand! I regulate the wire tension by finger pressure.

My thought was to make a layer and let it dry then wind
the next but the Q-dope was too think and I could not let it dry all the way
or the surface was too bumpy.
So you wound the next layer into the soft dope, and that means you got zero dope between the wires. It only filled some of the voids. Used that way, the dope will make the coil very solid and vibration-proof, but won't improve the insulation.

I now have thinner and think a number of
thinner layers would be possible. I was aiming for a 1-4 mils but have no
measurement It was a good % of the wire thickness.
It's probably very hard to get Q dope to form a layer of even thickness. You would have to spray it on, probably in many layers, while rotating the coil until it dries, so it doesn't flow by gravity. But you can't rotate the coil when the wire is hanging from it...

As Chuck points out I
don't know how close that would be to potting the coil
I wouldn't consider it a potting method, simply because the dope shrinks a lot while drying. Even if it fills out all voids while wet, it will contract and form gas bubbles when dry.

But you could in principle apply the same winding method, with application of a potting agent between layers, by using some potting agent that doesn't evaporate anything while drying, and so doesn't shrink. It could be epoxy resin, some kind of wax, tar, two-component potting silicone (not the common moisture-curing RTV sealant type), etc. With wax or tar you would need to work hot.

Basically you would brush a thick layer of potting agent onto each layer of wire, apply a porous insulator/separator sheet (fabric, nomex) so that the pottant squeezes through, then apply more potting agent in a smooth layer, and then wind the new layer into the layer of potting agent, so it squeezes up, and the wire compresses the whole stuff. If well done, that could result in a pretty good potting.

The problem is that it's messy! I love dry transformer winding...

For epoxy, the slow setting (1 hour working time) epoxy glue might work well.

or the effect of ozone on the wire I used.
If you get ANY corona at all, the transformer will eventually fail.

As for the multi-section bobbin I think we are talking about the same thing.
With the existing core there is not much room and the trick would be to get
the wire from the top of one section to the bottom of the next insulated
with out taking too much room.
It's only practical if you have enough winding length available. Bringing the wire from one section to the next is usually done by having an extra narrow space (one wire diameter) between two walls, just for that little piece of wire. Each wall has a slit in it, at different angular positions. So the wire comes off the top of the first sections, through the slit in its wall, into the narrow space, makes half a turn or so, then goes through the slit in the next wall, and starts the second section.

A variation of this is having single, relatively thick walls between sections, with slits cut diagonally into them. The wire goes from one section's top to the next section's bottom entirely inside that slit.

Okay, now I'm off to complete winding transformer #2. In a few hours I can tell you wich color of smoke I got this time! ;-)

Manfred

========================
Visit my hobby homepage!
http://ludens.cl
========================


Re: SHOULD THE SCALE ILLUM. ADJUST THE TRIG HOLDOFF ON A 2246? i DONT THINK SO...

 

I do not see any way short of a connector going to the wrong place or being
misaligned for the scale illumination control to affect anything except the
scale illumination because that is the only thing it connects to.

The scale intensity and A intensity are adjacent on the W900 connector
(schematic 7) so maybe it is misaligned. Further, the scale intensity is a 0 to
+15 volt signal and the A intensity signal is -2.5 to +2.5 volts. The input
multiplexor will only handle signals from -7.5 to +5 volts; if an input is
above +5 volts, then it may "leak" although looking at the schematic I do not
see how it would get into the holdoff control. This may depend on the order in
which the processor reads them though.

The other controls including the intensity controls and the holdoff control are
multiplexed both on their inputs and outputs so having them interact with each
other is a certainly possible if something is wrong there.

On 07 Sep 2014 16:12:24 -0700, you wrote:

Hello Thanks for having me. Can anybody confirm that according to the schematic for the 2246 the scale illumination board should not be able to adjust the trig holdoff when I turn the knob. I'm presuming this would indicate a powersupply issue? to add to that the readout intensity and the A intensity also adjust the trig holdoff. "Time signal to small" is the error. And the unit wont trigger.
Any Thoughts.
Thanks in advance.
David


Re: tantalum capacitor color code

Dale H. Cook
 

At 10:48 PM 9/7/2014, Kurt wrote:

What are the ratings of the tantalum capacitor in this photo?
Kurt -

What is that from? A look at the manual should clear up the matter.

Dale H. Cook, GR / HP Collector, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcity/radios/index.html