It tells me that something is drawing too much current.

Generally, it's a tantalum capacitor. The tantalum may NOT read a dead short, only some do. It could read low, draw an amp on a circuit where the circuit was supposed to draw 100 ma. I'd want to remove the fuse, check the power current vs. the fuse rating. Use the 20 amp range on a meter.

If it's not a tantalum, then something ought to be getting rather hot in operation.

The previous owner "fixed" the problem the same way that an "expert" electrician fixes a power problem by putting a penny behind the fuse.

Harvey

From: "Richard P via groups.io" <wb5nen=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: Friday, July 31, 2020 5:04:37 PM
Subject: Re: [TekScopes] Stuck switches on 453

Gents,

Thanks, all. I really don’t know if it’s the pot, or the combined switch,
that is frozen. One or the other. I can get spray into the pot, but it still
won’t move. The rotary switch on the back, however, is sealed tightly. I
will continue to attempt to get spray into the fool switches. There are two
of these combined pot/switches in the 453. Stay tuned.

Richard

I changed the 2 caps, as someone suggested. I’ve rechecked the voltages, and they are all good.
I’ve also re-cleaned the sockets. And nothing has changed. I’m waiting to modify the JAMMA connector to checks all that you guys suggested.
However, I did notice something maybe worth mentioning, and that might give you experts a clue as to what’s not right:
1- The plugin fuse (Fast 2A), blows every once in a while when I power the TM on and off 5-10 seconds apart Or so, to check if the “0” comes on in the same position, or at all. The previous owner had soldered a 4A fuse. Maybe because he had the same problem and thought 2A wasn’t enough... I don’t know why he’d do that. Grrr...
Does that tell you something?

Gents,

Thanks, all. I really don’t know if it’s the pot, or the combined switch, that is frozen. One or the other. I can get spray into the pot, but it still won’t move. The rotary switch on the back, however, is sealed tightly. I will continue to attempt to get spray into the fool switches. There are two of these combined pot/switches in the 453. Stay tuned.

Richard

I know how you feel! I still have two GPSDOs and a couple of Rb units sitting around (just in case), but although having at least seven stable zeros is nice, it doesn't make the scope you're working on any more accurate.  Unsubscribing from Timenuts made my life easier...
-Dave
On Friday, July 31, 2020, 09:43:19 AM PDT, Stephen <stephen.nabet@gmail.com> wrote:
On Fri, Jul 31, 2020 at 05:36 AM, Tom Gardner wrote:

Ah. A perfectionist tweaker :)

Yes, I am.  I like precision.  Maybe I do have an OCD.  😂

A quick skim of the schematic makes me think I would expect to see offsets on
the outputs.

Ok.

It is a time calibrator, not an amplitude calibrator. I'd be satisfied if the
peak-peak amplitudes are acceptably large.

Honestly, I haven’t had the time to check everything yet, but for what I’m using it for (mostly .1ms and 1ms time marks), it works like a charm.

It's worth building, if only partially.

As designed, it allows you to check AC voltage and phasing, bulk
supplies, power transistor beta (not directly), and provides a +5 and
+/- 15 volt general purpose supply.

Tektronix may or may not have made these, I don't know.  The description
suggests that it was intended for internal use as a testing tool.

If you do not want or need the regulated supplies, then bringing out the
transistors individually allows using a transistor tester.  A plugin
strip for a 5 volt regulated supply and pickoffs for the other pins (to
go to a front panel) could be made fairly easily, there are some designs
already that simply bring out the pins.  What you do with those pins is
up to you.

It's a design where you could throw a bit of technology at it and
automate some things, but that's an "up to you" kind of thing.

The pots are in the feedback circuit for the regulators and should
adjust the 15 volt supplies.

Harvey


On 7/31/2020 1:43 PM, Colin Herbert via groups.io wrote:

Does anyone know any more about this item? It has the ID# 067-1201-99
and I have the Tek "manual" for it as a pdf. There was also another
document which was termed "Construction Note". Did Tek make any of
these, or did they see them as totally for people to make themselves?
The "manual" that I have has the ID# 061-3001-00. The "Construction
Note" (which I also have a pdf of) seems to be exactly that as well as
being a Service Manual in that it gives some assembly information that
would be useful to a constructor. Both documents include a schematic,
but I cannot find any information on the function of two preset pots
R127 and R227. These are described in the Replaceable Electric Parts
List as "non-wirewound, 5K0, 20%, 0.5W" and I am assuming that they
set the +15VDC and -15VDC output levels respectively.

It looks like an interesting item.

Colin.

It's worth building, if only partially.
As designed, it allows you to check AC voltage and phasing, bulk supplies, power transistor beta (not directly), and provides a +5 and +/- 15 volt general purpose supply.
Tektronix may or may not have made these, I don't know.  The description suggests that it was intended for internal use as a testing tool.
If you do not want or need the regulated supplies, then bringing out the transistors individually allows using a transistor tester.  A plugin strip for a 5 volt regulated supply and pickoffs for the other pins (to go to a front panel) could be made fairly easily, there are some designs already that simply bring out the pins.  What you do with those pins is up to you.
It's a design where you could throw a bit of technology at it and automate some things, but that's an "up to you" kind of thing.
The pots are in the feedback circuit for the regulators and should adjust the 15 volt supplies.
Harvey
On 7/31/2020 1:43 PM, Colin Herbert via groups.io wrote:

Does anyone know any more about this item? It has the ID# 067-1201-99 and I have the Tek "manual" for it as a pdf. There was also another document which was termed "Construction Note". Did Tek make any of these, or did they see them as totally for people to make themselves? The "manual" that I have has the ID# 061-3001-00. The "Construction Note" (which I also have a pdf of) seems to be exactly that as well as being a Service Manual in that it gives some assembly information that would be useful to a constructor. Both documents include a schematic, but I cannot find any information on the function of two preset pots R127 and R227. These are described in the Replaceable Electric Parts List as "non-wirewound, 5K0, 20%, 0.5W" and I am assuming that they set the +15VDC and -15VDC output levels respectively.

It looks like an interesting item.

Colin.