Solartron 7066 EPROM firmware wanted

[Ludwik]

Hello
My meter has been having random resets during measurements for a long time.
This happened once every few months. Now I set the 10V range, turn off automatic range switching and do the test:
 - I apply negative voltage from the laboratory power supply, the readings are ok;
- I apply positive voltage, it measures up to about 0.6 V, then the display blinks strangely, the display turns off at about 2.5 V.
Please check whether the square wave at the TP201 measurement point should have an amplitude of 10V. Mine has 5V.
In the diagram, someone added that there is a 10V square wave.

The meter also sometimes had problems with stability, so I check all resistors.
After purchase, I replaced all electrolytic capacitors with tantalums and the improvement was significant.
He worked for several years and did many projects.

Thanks everyone for your help.

[bastl_r]

, I found 6 carbon resistors whose parameters differ significantly from the norm, e.g. instead of 68k there are 126k.

Wich ones did you mean? There are more than 6 resistors in it.

The meter also sometimes had problems with stability, so I check all resistors.

On my meter the last two digits was also not stable. The problems are, so i think at the pll wich is located under the little cover.

regards

[Ludwik]

It was the resistors in the integrator, because I have a problem with it.
I have to check them all. The best thing is: you measure the 1k resistor in the system and it shows 1.5k.
If you heat it up, it will be 1.2k when desoldering.

Pll I adjusted. is now stable. I checked with a frequency counter with a GPS pattern.

[Ludwik]

I continue to measure carbon resistors in my meter and came to the following conclusions:
1. resistors 10k and above, about 50% damaged - deviation above 20% or even 70%
2. other values ​​depend on the load, mortality approx. 25%
Conclusion - I will eventually replace all of them with metal 1%. Most in stock, processing capacity needed.


All documentation on the Internet lacks a diagram of the ohmmeter driver for 7065, diagram page designation 2.5. Does anyone have one of these ?

[bastl_r]

View all documents uploaded by DVM-James.
The missing pages are there.

[Ludwik]

This is the one page missing from the scanned 7065 documentation circulating on the Internet.
I downloaded from several different sources and it's the same everywhere.
The same incomplete file.

[DVM-James]

Is this the missing page ?  - it´s the same as on my 7066-servicemanual

[Ludwik]

Thank you very much, this is the page that was missing in the scans available on the net.
The meter is starting to come back to life, unfortunately the quality of the TTL systems available today leaves much to be desired.
When I install something other than the TTL 74F series in the meter there are problems with stability.
The regular ICs available on the market today are garbage that no one wants because they do not meet the standards. Only for children to play with.
I plan to restore it to better stability than the original, but that requires some work. Unfortunately,
all the resistors except the critical ones for measurement are carbon and fly off after heating.
Incidentally, I found an unstable ttl in the integrator and the fun begins.
I also have corrosion spots on the chips and the unfortunate carbon resistors and I wonder if someone kept this meter under the gutter.
The rest of the elements don't look bad, but why is only some of it corroded?
This meter, even in an unstable state, helped me solve several serious problems before one day it simply got offended and wouldn't go through the post.
For now, a handful of resistors, 4 diodes and 2 obvious integrated circuits. I didn't dig into it before because it measured quite ok for a cheap meter at the price of 4 and 1/2 digits.

Thank you all for your help, when I get it back to full working order I'll brag about it.

[Ludwik]

I look at the photo of the interior and I envy how clean it is. Speaking of a bad jumble of parts. In my case, it's only a TI (Motorola processor and memory, of course)