Stellavox main schematic

[chrissugar]

Hi all,

New member here. In fact not so new because I'm lurking here for a long time. I used in the past and still use tape recorders for studio work as stereo master recorders (the machines I have now: B77MKII, PR99MKII, 2x Studer A812).
I need some help from fellow tape enthusiasts. I'm looking for readable Stellavox SP7 and SP8 main schematic. I have some low resolution scans, and part values & numbers are almost unreadable for most of the parts.
Anyone can help me with this?
Thanks in advance.

chrissugar

[stellavox]

Chrissugar,

the main schematic is one page for the 7 and a bunch of pages for the 8 .

Email me @ stellavox@excite and I'll try to make you a clean copy - will also post them on the yahoogroups reel to reel website

Charles

[chrissugar]

Hi Charles

Thank you very much, I almost lost hope to find some good resolution files.
Will send you now an email.
Thanks again

chris

[gyrator]

Hi I'm a new member and my first posting here.

I'm very familiar with reel to reel mashines like ReVox, AKAI, Sony, ASC, Braun and today I have a new one with some trouble.

So I need your help to fix the problem of my Stellvox SP7 with Master 2Track Head-Block.

One of the input channel is broken, but the amplifier modules seams to be in right order.
There are a lot discrete components connect in free style around and on the mainboard, so it is nearly impossible to catch the broken component without an schematic that show what is how connected.

Is here someone who can help with an copy of the main wiring schematic?

Thanks in advance and greeting from germany

Thomas

[gyrator]

Hello all!

Again, what's happend, no answer at all?

If someone has an Service Manual or a part of it that shows the main schematic of an SP7, I can offer an Service Manual in portable document format (pdf) of an SP8.

Please, it would be very kind to make me this document available, cause it is to diffucult to fix the problem on my SP7 without an technical documentation at hand.

Regards

Thomas

[ironbut]

Hi Thomas, welcome to the forum.

If you've already checked with Charles (who was offering the schematic to Chris in the above post) and he wasn't able to help you, you might try contacting this Stellavox service guy.
http://www.audioprojpg.com/index.html

BTW, How common are Stellavox's in Germany? They hardly ever come up for sale here.

[gyrator]

Hi Ironbut,

thanks for your friendly words.

I tried in vain twice to contact chris and charles and I didn't get any responce or reaction from both.

Your stellavox link are leading to service in germany and swiss. By phone you won't get contact to Jean-Pierre Gurtner only the answer mashine is running at any time. Maybe the service is abandoned?

Further more I had a contact to Mr. Dingler, he offer a manual plus a schematic sheet for 35Euro plus tax. A lot of money for just some copy of paper.

And if I compare the service manual of an SP8 to an Studer or Revox Service Manual you get from ReVox or Studer much more and better technical documents for less money.

The stellavox is not much common in germany, nagra is much popular.
In germany the stellavox are hardly ever come up for sale, too.
I had an Nagra IV-S and under the aspect of technical construction the Nagra is realy much better than an stellvox.

regards

Thomas

[stellavox]

OK,

I just hooked up tag sale scanner and actually got it working - then scanned the main Sp7 schematic.  Tried to upload it to the files section of the yahoogroups reel to reel website but that appears full.  Anyone who wants a copy of it can Email me at [email protected].  All the various electronic functions were contained in separate, sealed modules in the 7 series and (fortunately for repair purposes) unsealed in the 8 series. 

For what it's worth - there were a few "varieties" of the Sp7 schematic - some with the European DIN microphone connectors, others with Cannon connectors.  there was also "A"  and maybe even a "B" version. The differences between them were primarily in the Pilot (film speed synchronization) circuit, which don't impact it's audio operation at all.  With the 8 series, the schematics were "broken" into several sheets for better readability. 

The original 7's had black front and side panels, later versions (including the 8's) went to the silver or brushed aluminum finish.  The Stellamaster versions had the special heads and flutter roller, a 128Khz bias/erase frequency (instead 61Khz) and a few minor changes in the record/playback compensation networks.

Main difference between the 7 and 8 series was the addition of space for three more AA cells so the B+ could be upped by 5 volts or so increasing the headroom.  Audio signal path was changed slightly and a more powerful motor added with a second ball bearing on the capstan shaft.  Original playback/record heads were made by Bogen - later on they changed to Nortronics.

And yes, components are "scattered" around the main board, and also hidden behind the left side plate - just to keep you on your toes. 

Charles

[gyrator]

Hi Charles,

thanks for your offer and you will get an email to make me the SP7 documents available.

Thanks in advance and regards

Thomas

PS: Then the failure is fixed I will tell it and pictured it here.

[stellavox]

Thomas,

I'd suggest putting the function switch on "test" and feed a 1 volt, 1Khz signal thru the "Diode" (pin 1=channel 1 or pin 4=channel 2) or "Aux" jack (pin 1=channel 1 or pin2=channel 2).  BTW I realized that these jacks are labeled and connected slightly differently between the 7 and 7A.

This input bypasses the microphone transformers and the preamp portion of the SPA/SOA modules and feeds the signal thru the main gain controls right into the record amp.  The signal then goes thru the SIZ bias trap modules right to the headblock where it should appear on pin 6=channel 1 or pin 13=channel 2.  If your using a scope to monitor the signal now turn the function switch to record and you should see the 1Khz riding on the bias voltage.

If things are OK here then input a much lower voltage into the microphone jacks.  This runs the signal thru the transformers ans the preamp section of the SPA/SOA modules.

Problem I've seen typically are caused by a bad module.  Record modules are on the right side, playback toward the front.

Charles

 

[gyrator]

Hi Charles,

if it is to far away to make a scan of the technical documents, please, please make just to pictures with an camera of the main sheet that shows the interconnection of all parts.
I had put an input signal 1kHz to DIN "Diode" input and at the same time I read out the signal from DIN "Diode" output. It shows that signal from CH2 at higher voltage (over -20dB) distorted. This is also without SBO SGC SPA+SOA and SWR, only the modules at the DIN connector were pluged in.

An interchange of SPA+SOA shows no difference, the broken channel is constant channel 2.
I assume that some of the signal capacitors are broken. A view of the interconection schematic would realy help to fix the problem.

Thomas

[stellavox]

Thomas,

As I said, Email me at [email protected] and I'll reply with the schematics.

Charles

[gyrator]

Hi Charles,

I had send an email on the 5th of june and also days befor as email and PM. Maybe my email is in the spam section of your aol account?

I will resend the email now twice again ( gmx.de and from my work office) .

regards Thomas


PS: My email is : gruenlilie@gmx(dot)net

Please set (dot) = .

[gyrator]

Hi Charles,

Many thanks for your help, I have just receive the jpg's from the main schematic of SP7.

I will tell here more then the problem is fixed.

regards

Thomas

[ironbut]

Hey Thomas,

Please keep us informed on your progress. Any technical information that you can relate in your repairs are of great value here.

There are plenty of "which machine sounds best" threads here and on other sites but having repair/modification tips on these "elite" machines will prevent other people from having to "reinvent the wheel"  and help keep these wonderful machine out of the dumpsters (which I'm sure has happened from want of technical support).