VGkids HP 6115a

[Vgkid]

Pictures to follow.
How do you remove the A1board?
I have all of the screws removed, but the wires are holding everything in.

[Vgkid]

Pictures are finally here!!!
This is how it was initially, no cleaning yet.
Looking down on the main board(A1)

Wait. That power resistor does not look very good, lets zoom in(side shot)

lets see what the damage is under the resistor.(It is fried, but still test in specs 1048 Ohms hmm)

Bottom of board(same area)

removing the big caps to test.(still in spec)

Control board

bottom of said board, those joints are grey.

[SeanB]

Snap, got the same series of capacitor right next to me, made probably in 1975. Still passed all the specs for the type, or at least the closest matches for the range I could get. Check the bung has not rotted, then screw them back in the right way round and carry on.

[Vgkid]

I was surprised that the Sangamo's were still in spec, as the paint had long since peeled off of the base(part that goes snug against the board). Of the 4 large silver snap caps I wil only have to replace 2 of them. 1 had the leads cut to short(oops, but it still measures good). The other has a reasonable good Cap value(though it is at the top of its 20%spec), but as a DF of .7X/.8X. That is about 7-8 times higher than the DF of the rest of them.

[gilbenl]

Were you able to power this unit up? What's the exterior look like?

I would recommend replacing all the caps. Both my 6920B and 6113A worked for about a day before caps started going. You're going to replace them all sooner or later.

You're probably going to need to desolder a few wires to take off the front panel. I find that easier than trying to remove meters, indicator lights, etc. You shouldn't need to desolder anything to do with the thumbwheels, however.

[Vgkid]

I ended up desoldering all of the wires attached to the A1 board,as soot covered most of it. I do realize that I might as well replace the ceramic caps. Some of their leads were really fragile.
The ebay seller actually powered it up, but the overload protection light was lit( the unit was set to max ol position).

[Vgkid]

Mega Necro bump. I have attempted to start cleaning the internals, from the combination of soot/other residue that was in the unit.
Found out that a mixture of hot water, dish soap, and ammonia dissolves ceramic capacitors, removes ink off components, and removes rust.
Pics to follow.

[Tomorokoshi]

I just worked through a 6114A, and a while back I worked on a 6227B.

On the 6114A the output voltage was unstable and didn't track with the selector. The grease inside the switch hardened and made the connection unreliable. I had to desolder the selectors from the board, take them apart, and clean the grease off. There are heat stakes that hold each individual selector together. I used alcohol to clean the grease, and then I used 3M Novec with silicone to relubricate them. All the contacts were gold plated. There is a contact strip that is not heat staked in, so be careful if you need to pull them apart.

Is that split resistor a "KELVIN" brand? I had those split on the 6227B.

[Vgkid]

^^^ Don't know, resistor practically destroyed itself.
Every time I enter my bedroom(where the electronics benches are) I'm reminded of my busted 6114A, and buried even further is the 6115A. Just so you know, my 6115 will never be original, I swapped its control board in order to fix a 6114A(that one exhibited a unstable zener reference.) I will be going through some rather harsh chemical/physical cleaning methods for this unit. Since this unit was involved in a fire, and let sit.
Note: I  dissembled this unit, and it has been sitting for years, I never even powered it on.*

We are looking at the back of the unit, Sooty residue covers everything, practically the whole machine will be tossed into the ultrasonic cleaner.

After a 15 minute bath in hot ammonia soapy water, followed by a scrub with the tooth brush, the board looks much better. Yes, I will replace those screws. Does anyone know if terminal shorting links is the corect term for those links. I'm going to improvise..

We now see the back of the terminal block. I wish I took a picture, in which the wires are running to a front switch???
Lets dive into the main A1 board.

This is the main board. After some light cleaning, and capacitor removal this is what we have.

After a very extended bath, we are left with a very much cleaner version of the above board, you can see the dissolving ceramic capacitors

Just showing the back half of the board. This ceramic capacitor looks new. Those flat flex cables cleaned nicely. Unfortunately they have a habit of breaking off at the board connector, when flexed.

The water from the terminal block side was not that bad, but the A1 board is disgusting. Though it easily contains dissolved components...
Question:
Is it ok to replace those ceramic disk caps with 630v(vs 400) film caps?
Also, do film caps have a lifespan, these are not going to be overly old
http://www.ebay.com/itm/100-Panasonic-ECQE6563KF-056uF-630V-10-Radial-Metallized-Polyester-Capacitors-/201151263426?hash=item2ed58cb2c2:g:LTMAAOxy3HJTGOvh