Topics

S-6 troubleshooting (S/N B044657): updated schematics required


Albert Otten
 

Hi Max,

I'm really too color blind for to read resistor values correctly. Since I measured 500R and at that time also didn't recognize RT43 as an NTC resistor I checked that R44 for having 500R colors. But it is 1k and your photo has the right labels now.
Note that the 1988 manual still shows the schematic of June 1982.

Albert

On Sun, Jul 19, 2020 at 03:15 PM, unclebanjoman wrote:


I've just added another photo, with annotations on the added and removed
components.
Matches with the latest schematic of rev. year 1988. VR18 (solder side) was
removed also.

Max


unclebanjoman
 

I've just added another photo, with annotations on the added and removed components.
Matches with the latest schematic of rev. year 1988. VR18 (solder side) was removed also.

Max


unclebanjoman
 

Hi Albert,

thank you for your efforts.
I've just created a new photo album:

https://groups.io/g/TekScopes/album?id=250556

where you can see the component location mismatched with the schematic.
I think I can get the pattern by hand, at that point...

Max


Albert Otten
 

Hi Max,

Now I made a mistake in reading "XB" in the parts list: R43T/R44 were introduced long ago in stead of removed. The .5 k replacement resistor I mentioned must be a new version NTR. The resistance indeed drops when heated.

Albert

On Wed, Jul 15, 2020 at 05:50 PM, Albert Otten wrote:


To be more precise, in my physical pcb version R40 is missing and in their
place there are two small little tantalum caps.
Hi Max, I think you are mistaken here. R40 (RT40 in the parts list) is the
small cap-like component just right-above the label R40 and left above C10 in
the PCB-layout and in the photo at Tekwiki. Just measure its resistance and
then put your fingers on it.
Moreover, I don't find any R43 and R44 on my pcb. The funny thing is that
they
are present on the schematic (1988 version) but not on the pcb layout of the
same manual...
RT43 and R44 were removed long ago and replaced by the 0.5 k resistor between
C10 and the trimcap, at least in my S-6 and in the photo at Tekwiki.

Albert


Albert Otten
 

To be more precise, in my physical pcb version R40 is missing and in their
place there are two small little tantalum caps.
Hi Max, I think you are mistaken here. R40 (RT40 in the parts list) is the small cap-like component just right-above the label R40 and left above C10 in the PCB-layout and in the photo at Tekwiki. Just measure its resistance and then put your fingers on it.
Moreover, I don't find any R43 and R44 on my pcb. The funny thing is that they
are present on the schematic (1988 version) but not on the pcb layout of the
same manual...
RT43 and R44 were removed long ago and replaced by the 0.5 k resistor between C10 and the trimcap, at least in my S-6 and in the photo at Tekwiki.

Albert


snapdiode
 

I don't have a print manual in my collection either. Only the PDFs I linked to.


unclebanjoman
 

I've already checked.
They are all equal. Moreover the 1983 version missing half of schematic page.
To be more precise, in my physical pcb version R40 is missing and in their place there are two small little tantalum caps.
Moreover, I don't find any R43 and R44 on my pcb. The funny thing is that they are present on the schematic (1988 version) but not on the pcb layout of the same manual...

I'll try to ask Dave of Artekmedia if he has a suitable copy of the manual.

Max


snapdiode
 

There are three S-6 operating manuals here

http://w140.com/tekwiki/wiki/S-6

Maybe one of these will work for you. I hope your hybrid isn't cracked.


unclebanjoman
 

Hi all,
I started troubleshooting my S-6 head, using a 7S11/7T11 pair with extender for the S-6.
Symptoms are: large negative offset, exaggerated amplitude and waveform horribly distorted at any frequency.
Rotating the trims have negligible effect (just to exclude some wiper's contact problem).
I start to check the biasing circuit (U20A/B) and the series resistors between +50 and -50V but I discovered that the schematic and the pcb layout does not coincide with the documentation I have.
The A-4 preamp board is marked 670-1402-01; the strobe board is marked 670-1403-03. The S/N marked on the housing is B044657.
Anyone have an updated scheme?

Moreover, I noticed that on the schematic there are are two distinct grounds. But i don't know how the JFET may work if the gate is referenced to one ground (the one with the triangular shape) and its drain is connected to U20D that use the ground coming from the power supply interface..
Any ideas? I'm a little puzzled.

Thanks,

Max