Date   
Re: 310A scope : serial number oddity ? Ideas ?

J Mcvein
 

However the big downside is that there is a thin layer of some very fine >"powder", must be some oxide, yellow-ish/green-ish in colour, covering >just about every single screw, head/...
Cadmium! So common to electroplated hardware of the time.Toxic, don't eat, inhale, etc.  Wash hands.  Plants thatused to plate it here (US), were shut down by the 1970's

JimMc

On Monday, September 10, 2018, 4:45:49 PM PDT, Vincent Trouilliez <vincent.trouilliez@...> wrote:

On Sun, Sep  9, 2018 at 05:51 PM, ditter2 wrote:
[..] As for the BNC versus UHF connectors on your unit, they may have been upgraded.
[..] Tek offered a mod kit for several of the tub instruments to convert to BNC connectors.
[..] You can probably get a good idea of the manufacturing date  by looking at the date codes of the large electrolytic caps.
[..] Many tubes also have date codes.

- Steve
Hi Steve,

I didn't want to open up the scope, as I have already a couple scopes I am working on at the moment, spread all over the bench... I wanted to keep the surprise of the 310A for later, when I actually have time to work on it. But.... it would be rude not to reply to you, and it gives me a good excuse to open it up sooner than I planned, so thank you ! LOL ^^

I think the BNC was fitted at the factory... as my scope is a late model it appears, actually so late it might as well be early solid state ! LOL

I had no luck with the tubes... pulled a dozen of them, at random places, from various manufacturers (Brima, Toshiba, Mullard, General Electric), none of them had date codes ! Bummer. Looked at the "cans"... luckily all very easy to access. 5 of them. 4 had date codes on them, all consistent : one was marked "1366", and the others read, in clear, "March 1966". So, end of March 1966 it is !

I am still a bit perplex : how can such a late 310A, have a serial number as low as #1239 ?! Baffles me...

This first peek inside the scope gave me preview of what I can expect when I get round to restoring this puppy... mixed feelings ! :-/
Basically looks brand new inside, even found a couple rubber grommets whose rubber still looks and feels as good as new, still a deep shiny blakc, still supple, and I am not even kidding. How can rubber survive 50+ years this well, no idea. Zero dust, all ceramic strips, components and solder joints, all look sparkling new.

However the big downside is that there is a thin layer of some very fine "powder", must be some oxide, yellow-ish/green-ish in colour, covering just about every single screw, head, thread, electrolytic can backing plate, every pot and trimmer (some have their shaft seized !), as well as all the little "lugs" on the tube sockets, where the anti-vibration copper "clip"/retainer attaches to, whatever it's called.
Boy I will have some fun sorting all this out ! Hopefully there exists some chemical/product that can dissolve all that oxide efficiently/easily... then I will have to remove all the pots to dismantle/open them, to free the shafts and make sure the wipers in them are OK.

Lots of fun ahead ! .....

Kudos to the engineers who managed to cram so much stuff in so little space, it is EXTREMELY tight in there !  :-O
Kudos as well to all the little hands at the factory who were tasked with assembling these things ! They deserve a medal...




Vincent Trouilliez

Re: 310A scope : serial number oddity ? Ideas ?

Vincent Trouilliez
 

On Mon, Sep 10, 2018 at 06:49 PM, J Mcvein wrote:
Cadmium! So common to electroplated hardware of the time.Toxic, don't eat,
inhale, etc.  Wash hands.  Plants that used to plate it here (US), were shut down by the 1970's

JimMc

Thanks Jim !

Now that I know what it is... I can go ask the chemists out there what chemicals I might use to "neutralize"/dissolve it... well if there is one that is, crossing fingers ! :-/


Vincent Trouilliez

Re: 310A scope : serial number oddity ? Ideas ?

Jim Ford
 

Yeah, we're supposed to wear gloves when handling the green plated military connectors at work because they contain cadmium, but nobody does.   We do wash our hands afterward, though.
Jim


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Vincent Trouilliez <vincent.trouilliez@...> Date: 9/10/18 7:10 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 310A scope : serial number oddity ? Ideas ?
On Mon, Sep 10, 2018 at 06:49 PM, J Mcvein wrote:
Cadmium! So common to electroplated hardware of the time.Toxic, don't eat,
inhale, etc.  Wash hands.  Plants that used to plate it here (US), were shut down by the 1970's

JimMc

Thanks Jim !

Now that I know what it is... I can go ask the chemists out there what chemicals I might use to "neutralize"/dissolve it... well if there is one that is, crossing fingers ! :-/


Vincent Trouilliez

Re: 310A scope : serial number oddity ? Ideas ?

John Griessen
 

On 9/10/18 6:45 PM, Vincent Trouilliez wrote:
However the big downside is that there is a thin layer of some very fine "powder", must be some oxide, yellow-ish/green-ish in colour, covering just about every single screw, head, thread, electrolytic can backing plate, every pot and trimmer (some have their shaft seized !), as well as all the little "lugs" on the tube sockets, where the anti-vibration copper "clip"/retainer attaches to, whatever it's called.
I would not dissolve the cadmium yellow, just find something to pint it with to bind it in place. Like acrylic clear paint applied with a brush in a thin mix. Dissolving it will not yield results since there is a thick layer of shiny white metal underneath it ready to turn into cadmium yellow as soon as exposed to the air.
--
John Griessen

Re: Tek 7603 Followed Me Home

bobh@joba.com
 

Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and is the only one that doesn't charge up to some value using the cap test position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to ultimately replace all the cans in the back section.  I may use two 1000ufd 100v caps to replace the 1800 ufd 75 volt C808 on the -50 unreg.  In this case the can is connected to the -50 unregulated rather than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a replacement cap for testing while waiting for the ones I ordered.

Bob.

On 9/9/2018 9:57 AM, Chuck Harris wrote:
My guess would be the -50V unregulated supply's
filter capacitor is no longer any good.

His VAC readings are certainly Vrms as read by his
DVM, so they are 2 x 1.4Vp-p, or in other words, he
has: 13Vrms x 2.8Vp-p/Vrms, or 36Vp-p ripple on a 50V
unregulated supply. No way that can work!

-Chuck Harris

John Griessen wrote:
On 9/9/18 10:11 AM, Robert Hay wrote:
I'll re-check the voltages
50 and -50 being actual 44 and -44 is the big clue.

Chuck was saying you probably have a very much changed component contributing
the the +44 and -44 regulated voltages, so some individual component volt level
measurements are next to do.

Them both being the same 44V suggests some protection feature of the circuit is
kicking in because some
filter caps are too leaky, but not shorted or open yet.
Look for bad caps there after the regulator.

The -52 for unregulated 50 is not likely enough headroom to regulate to 50V, so that
is suspect also.
Look for bad caps there before the regulator.



Re: Bringing up a Tek 555 dual-beam scope

John Miles
 

True, the "bumble bee" caps in the signal path will likely be bad and need
replaced, but there is no danger in turning on the scope with these in the scope
if they are bad, and troubleshooting to find them is usually fairly easy.
I don't know about the 5xx scopes, but if you've worked on vintage radios you've probably seen cases where a leaky interstage coupling capacitor dumps a lot of positive bias onto a grid from the previous stage's plate circuit. The end result is excessive current through the plate (possibly lighting it up cherry-red) and the audio or IF transformer it drives.

Opinions will vary but I think it's better to get all of those paper caps out of the device before you even hit the power switch, certainly before you let it run for more than a few minutes. I agree with the "wait and see" approach with electrolytics, though, since there's no guarantee that NOS electros will be any better than the old ones.

I do remove the covers before I power up to scope the first time to check for
smoke. If you see smoke, resist the urge to immediately turn off the power.
The larger carbon comp resistors need several seconds of giving off smoke
before they burn or even discolor. But the value may change considerably when
they over heat. I had this happen a couple of times, and found it very difficult
to find the specific resistor to troubleshoot because I did not let it burn long
enough.
An IR camera is nice for this. You can watch an entire chassis or PCB on initial powerup and spot problems before the smoke starts, possibly months or years before. And overheating components will stay that way long enough to be identified.

These cameras used to be ridiculously expensive, but you can get smartphone IR camera adapters from companies like Seek or FLIR for a couple hundred bucks now. Not the sort of tool you use every day, but also not the sort of tool you will want to give up.

I always turn the focus knob to the stop and intensity down before initial power
up. I have had a few scopes with problems in the CRT grid circuit that resulted
in high beam current even with the intensity turned down, and if the CRT was
focused, the phosphor would likely be burned.
That's a good idea.... and IMHO, carbon resistors in focus dividers are another good part to replace "just because."

-- john, KE5FX

Re: 310A scope : serial number oddity ? Ideas ?

David DiGiacomo
 

I am still a bit perplex : how can such a late 310A, have a serial number as low as #1239 ?! Baffles me...
There's no mystery. The serial numbers were not coordinated between
the manufacturing sites. Your scope was the 1239th 310A made on
Guernsey, but there could have been a million units made in Beaverton
before that.

Re: telequipment s54a trace too low on y

james.simpson54@frontier.com
 

I took a quick look at that portion of the schem. and noticed that. One thing I don't understand is on all of the schematics it has what looks like test points and they are labeled with a number within a circle. They start with #1 on the first schem. and then 2,3 and so on. The schem notes "numbers within the circle denotes tag no. on p.c. 70" I was hoping these were test points and somewhere there would be a list with what the voltages were. Or I was hoping on the schem. it would show voltages at certain points "along the way" (I think the d54 schem. has voltages shown at certain areas)) None the less, I need to get it opened up and get a look at it. Wed. Night I go see Travis Tritt and Charlie Daniels band so I have to get mentally prepared for it.

Re: Tek 7603 Followed Me Home

Chuck Harris
 

I am not sure what you are saying when you say that
C808 tests at 0.0 ohms. Do you perhaps mean 0.0 uf?

Typically, when ripple gets to be that excessive, the
capacitor's internal connection has been etched away
and is open circuit, or the capacitor's electrolyte
has dried up. The capacitance goes to near zero uf.

As a temporary fix, you can get back in business by
paralleling just about anything across the original
capacitor at its terminals. Even as little as 1/10th
the correct value will sometimes be close for the circuitry
to limp along and work. Tektronix was very generous
with its margins.

-Chuck Harris

Robert Hay wrote:

Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and is the only
one that doesn't charge up to some value using the cap test position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to ultimately replace
all the cans in the back section. I may use two 1000ufd 100v caps to replace the
1800 ufd 75 volt C808 on the -50 unreg. In this case the can is connected to the -50
unregulated rather than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a replacement
cap for testing while waiting for the ones I ordered.

Bob.

On 9/9/2018 9:57 AM, Chuck Harris wrote:
My guess would be the -50V unregulated supply's
filter capacitor is no longer any good.

Re: Tek 466 analog storage

EB4APL
 

Toby,

There are three 466 manuals. If yours is the one named Tektronix 466 Service Manual (PDF, OCR) <http://w140.com/tekwiki/images/c/cc/070-1753-01.pdf>, I can improve it somewhat if you don't mind. I can number the pages to reflect the original numbering and also I can add markers to point to the pages listed in the Table of Contents. I always do that in my own equipment manuals to easy the finding of schematics and alignment instructions. It'll take quite time but I'll do it if anybody is interested.

Regards,

Ignacio, EB4APL

El 03/09/2018 a las 18:32, toby@... escribió:
On 2018-09-03 11:16 AM, Roger Evans via Groups.Io wrote:
There is a very decent PDF manual at w140.com/tekwiki/wiki/466.
That would be the one I scanned. I took a lot of care to make sure it's
clear -- if you find any problems, let me know, I still have the
original files and paper manual.

--Toby



For serious fault finding I print off a few pages, sometimes as two
sheets stuck together, and make a note on these where to find other
schematics and layout pages. It looks like all the lower voltages get
their reference from the +65V that you will find just below the +140V
supply on schematic <11> Power Supply and Distribution. If all of your
lower voltages are off by the same fraction eg all low by 20% it could
just be that the +65V is off spec and everything else is OK. If you
want I can talk you through some of the stages but I am far from being
an expert and you will have to wait until after our holiday!
Roger




Re: Tek 7603 Followed Me Home

Kevin Wood G7BCS
 

If it helps, I had a 7603 fault due to one of those reservoir caps failing
and, when I got round to checking them, most of the caps on that rectifier
board were on their way out, so I changed them all.

That doesn't mean yours will be, of course, and I'm not generally an
advocate of "re-capping" devices en-masse, but my recollection is that it
was not that easy to get to the board and change the caps either, so it
might be a false economy to change just one or two.

Beware that several of those caps have multiple can connections to the
board and, on some, I think they are used as "jumpers" to connect traces
across the board. If replacing with caps of a different form factor, which
will probably be almost inevitable, you might need to insert jumpers
across some of the can connections. Apologies if I'm delivering lessons in
"egg-sucking"!

Kevin
G7BCS

Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and
is the only one that doesn't charge up to some value using the cap test
position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to
ultimately replace all the cans in the back section.  I may use two
1000ufd 100v caps to replace the 1800 ufd 75 volt C808 on the -50
unreg.  In this case the can is connected to the -50 unregulated rather
than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a
replacement cap for testing while waiting for the ones I ordered.

Bob.

Re: Tek 7603 Followed Me Home

tom jobe <tomjobe@...>
 

Hi Chuck,
I think he means it appears to have a dead short (or close to it) and this is why I say that:
I have been following this 7603 thread, and had printed the power supply schematic out on large size paper to study as I followed this interesting thread.
Yesterday I thought my interest in this 7603 thread might also be a good excuse to try to fix a 7603 I have that has a large note on it about blowing the fuse instantly when it gets powered on.
There did not appear to be any short on the primary side of the main transformer, so soon this 7603's power supply was out and apart so I could check the large filter capacitors for ESR and resistance in the circuit. C808 appeared to be a full short in circuit to an ESR meter and to an ordinary Fluke DMM.
A study of the circuitry around C808 shows several other paths a short circuit could come from with everything still in the circuit, and that is where I left my search yesterday.
I figured I would study the power supply schematic and see what else I could figure out before removing any of the possible problem components.
This morning I was quite surprised to see Robert's report of finding a shorted C808 in his 7603!
Then when I saw Chuck's question this morning... I realized that my thinking there could even be a dead short in an aluminum electrolytic cap might need to be re-thought.
Other details:
This capacitor is part of the filtering of the 50 VDC supply immediately after the full wave rectifier. This transformer winding is center tapped to ground and two capacitors are used on the plus and minus outputs of the rectifier to ground. This C808 is on the negative side to ground, and a C909 on the positive side to ground. These two capacitors are identical (1800 uF/75 v) and C909 does not appear to be shorted when tested in circuit (several thousand ohms) which left me 'scratching my head' at the end of yesterday's investigation.
tom jobe...

On 9/11/2018 5:15 AM, Chuck Harris wrote:
I am not sure what you are saying when you say that
C808 tests at 0.0 ohms. Do you perhaps mean 0.0 uf?

Typically, when ripple gets to be that excessive, the
capacitor's internal connection has been etched away
and is open circuit, or the capacitor's electrolyte
has dried up. The capacitance goes to near zero uf.

As a temporary fix, you can get back in business by
paralleling just about anything across the original
capacitor at its terminals. Even as little as 1/10th
the correct value will sometimes be close for the circuitry
to limp along and work. Tektronix was very generous
with its margins.

-Chuck Harris

Robert Hay wrote:
Chuck,

C808 on the -50 v unregulated is the only cap that tests at 0.0 Ohms and is the only
one that doesn't charge up to some value using the cap test position on my Tek DMM916.

I ordered some replacement caps although I am not sure whether to ultimately replace
all the cans in the back section. I may use two 1000ufd 100v caps to replace the
1800 ufd 75 volt C808 on the -50 unreg. In this case the can is connected to the -50
unregulated rather than ground so I need to tie all those loose ends together.

I'll hit up the local electronic surplus tomorrow to see if I can find a replacement
cap for testing while waiting for the ones I ordered.

Bob.

On 9/9/2018 9:57 AM, Chuck Harris wrote:
My guess would be the -50V unregulated supply's
filter capacitor is no longer any good.

Re: 067-0587-01 Calibrator Fixture

Fabio Trevisan
 

Hello Tomas,
It may be a long shot, but here goes my idea...

Any ideas about the decreasing separation of lines when I increase repetition
rate?
So you have a 7704A mainframe and no other (7K series) to compare to... and using the calibrator at highest speeds, the vertical steps are closer...
Well, it may be that your mainframe's middle frequency response (the higher repetition rate of the Calibrator's GAIN Test mode, is just middle freq to a 200MHz scope) is set too low... and this "lack" of middle freq response is being compensated by an increased middle frequency response in your vertical plugin.
Overall, the frequency response of the set: Vertical Plug-in + Mainframe can be correct because they have been calibrated as one set and, would this be an integrated scope, this would be just fine...
But on a modular scope, one doesn't just want to have the end-to-end response right, but to make sure that the Vertical Output Amplifier (i.e. the Mainframe) have a flat frequency response (and that's where the calibrator comes in), and then, after one knows the MF's freq response is right, the Vertical Plugins are calibrated for even frequency response.

There's hardly anything that can be wrong with the calibrator's staircase generator that could explain a difference in deflection factors when it's set to a higher repetition rate (in comparison to itself, set to a lower repetition rate) but, I can think of two ways to rule this out:
1. Using the calibrator's leveled sine wave test mode (you will need to source a sine wave from an external generator).
If this hypothesis is right, as you sweep from a lower frequency to a higher frequency while ensuring that the sine-wave is leveled using the calibrator's CW Leveled indicator, you should notice a decrease of the sine wave's waveform amplitude on the screen (at some middle frequency, compared to the calibrator's higher repetition rate).

2. If you have another scope, whose frequency response is known correct up to at least 1MHz or so (not much), you can probe the + and - outputs of the calibrator (either using an extender, or probing the signals at the mainframe's back-plane's pins A11 and B11) and while changing from the lower repetition rates to the 1MHz repetition rate, taking note of the steps' voltage difference.
If there's no voltage difference between the steps, when changing from lower rep. rates to the 1MHz repetition rates, then there's nothing wrong with the calibrator, and it's your mainframe who's uncalibrated.
It's not that much difficult to tap into the MF's left bay's back plane pins A11 and B11... The leftier of them is immediately reachable, while the other one (the inner column of pins) can be reached with an insulated piece of rigid wire (I use the wires taken out of an UTP network cable) with just a mm of the insulation stripped off. You can insert the wire between pins 11 and 12 of the outer column, inclined down so that it can touch the inner pin 11.
Ideally, on your test scope, you should connect both your probes and measure them diferentially, and, at this kind of frequency, even using a regular dual channel scope in differential mode will do well enough to confirm if the problem is on what's coming out of the Calibrator, or if it's the MF that is not correctly calibrated.

Well, that's my hunch only.

Rgrds,

Fabio

Re: Tek 7603 Followed Me Home -- shorts

John Griessen
 

On 9/11/18 9:17 AM, tom jobe wrote:
A study of the circuitry around C808 shows several other paths a short circuit could come from with everything still in the circuit, and that is where I left my search yesterday.
To debug shorts all together a milliohm meter is handy. HP3456A is good...but remember that it puts out a negative voltage when in ohms mode. Seeing the milliohms difference as you move a sharp tipped probe along will help zero in on a current path.

Re: Tek 466 analog storage

toby@...
 

On 2018-09-11 10:10 AM, EB4APL wrote:
Toby,

There are three 466 manuals. If yours is the one named Tektronix 466
Service Manual (PDF, OCR)
<http://w140.com/tekwiki/images/c/cc/070-1753-01.pdf>, I can improve it
somewhat if you don't mind. I can number the pages to reflect the
original numbering and also I can add markers to point to the pages
listed in the Table of Contents. I always do that in my own equipment
manuals to easy the finding of schematics and alignment instructions.
It'll take quite time but I'll do it if anybody is interested.

Regards,

Ignacio, EB4APL
Up to you. If you can do that with zero quality loss, please submit the
new version to TekWiki (I believe you can get an editor account from Kurt).

(I don't OCR anything myself, but if I recall correctly, a friend OCR'd
my scans and then I uploaded his version, so that file you mention is
probably based on mine.)

--Toby

Re: Tek 7603 Followed Me Home

Chuck Harris
 

That wouldn't explain why he reports the voltage across C808 is about
-52V with about 30Vp-p ripple.

I think he meant 0.0uf... and the rest of my post was with that thought
in mind.

-Chuck Harris

tom jobe wrote:

Hi Chuck,
I think he means it appears to have a dead short (or close to it) and this is why I
say that:
I have been following this 7603 thread, and had printed the power supply schematic
out on large size paper to study as I followed this interesting thread.
Yesterday I thought my interest in this 7603 thread might also be a good excuse to
try to fix a 7603 I have that has a large note on it about blowing the fuse

Re: Tek 7603 Followed Me Home

tom jobe <tomjobe@...>
 

Thanks Chuck,
Whoops... I do remember him saying he had the -52 volts, another little detail that sailed right over my head!
It must be those damn birthdays that keep flying by, the 78th just went by.
tom jobe...

On 9/11/2018 8:11 AM, Chuck Harris wrote:
That wouldn't explain why he reports the voltage across C808 is about
-52V with about 30Vp-p ripple.

I think he meant 0.0uf... and the rest of my post was with that thought
in mind.

-Chuck Harris

tom jobe wrote:
Hi Chuck,
I think he means it appears to have a dead short (or close to it) and this is why I
say that:
I have been following this 7603 thread, and had printed the power supply schematic
out on large size paper to study as I followed this interesting thread.
Yesterday I thought my interest in this 7603 thread might also be a good excuse to
try to fix a 7603 I have that has a large note on it about blowing the fuse

Re: Tek 7603 Followed Me Home

bobh@joba.com
 

Chuck & Tom,

I just rechecked the unreg. -15v Ohms across C808 and I think I just screwed up on that measurement.  The + side of the cap is grounded and I think I must have just measured from ground to ground.  Now I get about 7k Ohms from can case (-) to ground. And, my $10 component identifier says it's a diode which makes sense because of the rectifier circuit through that sec winding.

And Kevin, thanks for your ideas.  I was aware that the four can connections make up parts of the circuit and I will probably needed jumpers.  But, I need all the help and ideas to stay on course.

Thanks guys,

Bob.

On 9/11/2018 8:27 AM, tom jobe wrote:
Thanks Chuck,
Whoops... I do remember him saying he had the -52 volts, another little detail that sailed right over my head!
It must be those damn birthdays that keep flying by, the 78th just went by.
tom jobe...

On 9/11/2018 8:11 AM, Chuck Harris wrote:
That wouldn't explain why he reports the voltage across C808 is about
-52V with about 30Vp-p ripple.

I think he meant 0.0uf... and the rest of my post was with that thought
in mind.

-Chuck Harris

tom jobe wrote:
Hi Chuck,
I think he means it appears to have a dead short (or close to it) and this is why I
say that:
I have been following this 7603 thread, and had printed the power supply schematic
out on large size paper to study as I followed this interesting thread.
Yesterday I thought my interest in this 7603 thread might also be a good excuse to
try to fix a 7603 I have that has a large note on it about blowing the fuse


Re: Tek 7603 Followed Me Home

John Griessen
 

On 9/11/18 11:01 AM, Robert Hay wrote:
Chuck & Tom,
I just rechecked the unreg. -15v Ohms across C808 and

The mismatch of the units stops this from being helpful.
Can you tell us what you mean about unreg ohms of a capacitor? Or correct the mistake?

Do you mean volts across c808?

It's gotta match up to give an answer that means anything or helps anything.

Re: Tek 7603 Followed Me Home

bobh@joba.com
 

Hmm, poor reporting on my part.

 I measured the _Ohms_ across C808, which is on the (damn not -15) -50 volt unregulated, and it measures about 7k Ohms.  This was to correct my previous email saying I had measured 0.0 Ohms.

Bob.

On 9/11/2018 9:27 AM, John Griessen wrote:
On 9/11/18 11:01 AM, Robert Hay wrote:
Chuck & Tom,

I just rechecked the unreg. -15v Ohms across C808 and

The mismatch of the units stops this from being helpful.
Can you tell us what you mean about unreg ohms of a capacitor?  Or correct the mistake?

Do you mean volts across c808?

It's gotta match up to give an answer that means anything or helps anything.