Stabilock 4010 problem

[PA0PBZ]

Hi,

I got myself a Stabilock 4010 test set, mostly because I always wanted one and this thing was cheap According to the previous owner the magic smoke escaped and indeed when I picked it up it smelled like a campfire. After a good hour with screwdrivers, eyes and nose I found that the only tantalum cap in the whole instrument disintegrated, and of course it was hiding behind some screening:



After fixing that I tested the thing and only found one problem. It has 4 frequency bands: 0.1-40Mhz, 60-100Mhz, 140-180Mhz and 420-480Mhz, the lowest band is created by mixing down the 140-180Mhz one. The output is fine but the built-in frequency counter displays 140Mhz too high. According to the service manual a signal is created that indicates if the frequency is below 40Mhz:



This is fed to the output stage so it knows when to mix down, and it is also fed to the counter to subtract 140Mhz from the input:



The only thing is... the counter in my 4010 does not have this circuit, and the 'below 40Mhz' signal is not connected to the counter. So I have no idea how it should work, and I could not find any documentation showing the counter I have. It's a long shot but does anyone have documentation that matches the 4010 I have here?
 
The documentation I used is available in several places and the best copy I found is here: https://doc.xdevs.com/doc/SOLARTRON/stabilock%204010-4011-4020-4022.pdf (Warning: 70MB!) The counter pcb is at page 48, my pcb is missing D13, D14 and D15 and the layout is different too.

[PA0PBZ]

Since I have no down mixer on the counter board and the signal for the counter comes from the synthesizer (they call it decade) I decided to open that up and see if maybe it is hiding in there. Unfortunately not, the whole thing corresponds with the documentation. However I did make an interesting find. While I'm quite sure the synthesizer has not been opened for 40 years, well, look at the picture. Unfortunately no empty sockets so I wonder what happened in production...

[bd139]

I've seen that before in an old Heathkit counter. There was some old sticky tape floating around too. The conclusion I came to is that the original owner had blown the prescaler IC up before and bought two spares. The left over spare he taped inside the chassis. This was dislodged by transporting it over time.

[PA0PBZ]

I've seen that before in an old Heathkit counter. There was some old sticky tape floating around too. The conclusion I came to is that the original owner had blown the prescaler IC up before and bought two spares. The left over spare he taped inside the chassis. This was dislodged by transporting it over time.

I can imagine that, but in this case it's an ordinary 7400 so I don't think it was ment to be a spare.

[bd139]

Interesting mystery then. Probably an answer we'll never know. Wondering if it's like a wishing well? Chuck an extra 74xx in for luck 

[PA0PBZ]

Alright then, I found a users manual for the 4010:

Note: Over the range 10 KHz . . . 40Mhz the counter displays 140Mhz too much, since it is indicating the non-demixed oscillator frequency in this case.

I guess they corrected this in later models, thanks Schlumberger 
At least I now have a lot of knowledge about the working...

[fozzyvis]

Hi PA0PBZ,

Any chance you could send me the manual?

I've got a 4010 coming over (in unknown condition) and couldn't find a user manual, only the service manual. The link to xdevs is dead, and their listing don't show that manual anymore either.

Thanks,

Dieter ON4DD

[PA0PBZ]

Hi Dieter,

I checked my archive and apart from the service manual I have one other manual that seems to be a combination of a user and technical manual.
It can be downloaded here: https://nvhrbiblio.nl/schema/Schlumberger_4010_usr.pdf
I hope your German is up to the task

[fozzyvis]

Ah right, I did find that document, but I thought there might have been a complete user manual available somewhere.
TBH my German is *very* rusty but "Flemish" is somewhat related to German so I should be able to figure some things out...

Thanks!

[PA0PBZ]

Hi,

I have a dead tree version of the 'operating manual', it's like 100 pages double sided, not sure if I want to scan that manually