Studer A810 stuck in "Safe"

[sredwine]

I have recently brought an A810 back from the dead-many Frako caps and a backup battery later and it was working great. I left it on the shelf for several days while waiting on new meter lamps. I put the lamps in and it will not come out of "Safe" mode no matter what. Checked all the dipswitches and jumpers, checked for pinched wires-nothing. Does any body know what's wrong?

[sredwine]

OK, I've answered my own query! The Basis board foil that feeds 5.6V to pin 24 on both record boards had opened while on the shelf-this pin sends a signal back through a 1K ohm resistor via pin20 on each record amp board that lets system know it is in place-no record board, no "Ready"! I had replaced C10 on gthe basis board-the foil in question had opened while sitting on the shelf-apparently my removal of the old C10 had weakened the foil just enough to cause it to open later.

[docb]

Good sleuthing, that sounded like what the old TV repairs guys used to call a tough dog.

[eugen_syd]

To all A810 owners

This happened to me too on the recapping process. Take good care on replacing the capacitors. It is very easy to damage the layer behind on push in of the capacitors, traces are very narrow. I felt like I've done a good job but for more than one month I've been confronted with the same problem SAFE only. Finally I managed to test all my boards in a friend machine and all worked perfect. One think left THE MAIN BOARD. I managed to obtain another board via e-bay, recapped with much more care and BINGO. All problems gone!!!!!

Regards from Australia,
EUGEN IOV

[Ki Choi]

Good to hear happy ending Studer stories.

I still get amused and surprised at the level of design thoughts that went into Studer machines every time I have to deep dive into them with issues.  However there are few things that I wish they had done differently.

From top of my head:

1) Use of the dreaded Frako caps...  I am sure the cost was an important factor for the volume of electrolytic caps they used when tapes were in higher demands but using a little better quality electrolytic caps would have save thousands of hours over the years.  A friend restores old German radios from 30's and 40's. Most of the electrolytic caps are still good in them even today after reforming them but the Frakos and small blue Philips caps in Studers are guaranteed to fail...

2) Use of poor quality inductors...  In most of the capstan control boards for Studers, age will disintegrate ferrite core holding "wax" or plastic material, and they go out of adjustment.  The moment one tries to put an adjustment screw on them, they fall apart... and no replacement inductors available.

3) Poor quality double sided boards ... many have found that removing components without fully melting the solder around the pins and leads while pulling on the part will most likely damage the through hole traces.  It is a bigger problem for A80 boards.

4) Use of rechargeable MPU back up batteries... killer for A810s with 100% leaky batteries that will eat into the socket pins and  the acid fume from the batteries dissolving circuit copper traces on the board while looking ok on the surface.

5) Use of switching power supply design for audio sections... this is true even for the top model - A820s.  One of the reasons why external preamps sounding better.

Oh... I am sure there are more but enough for today!

Ki

[eugen_syd]

Hi Ki,

We all appreciate a lot your assistance and knowledge on STUDER/REVOX. I could not succeed without your help and thank you again for all your support.
All your points are very valid but what I wanted to add is the fact that most of the European manufacturers on that era used local made capacitors (could be a political reason... who knows). We all know that electrolytic capacitors like ELNA, NICHICON, PANASONIC last much longer but I never saw them used in STUDER or REVOX. Wonder why a company of that magnitude did not want to use the best capacitors in the world???
Regards from Australia,
EUGEN IOV

[Waltzingbear]

Studer did use Panasonic FC caps in the very last A827MCH decks, gold edition.

Mostly you need to consider the time frame of when these decks were designed, the early 1980's. I wouldn't trust many of the Panasonic caps from that time period. Some of the Frako caps were fine, but it seems to me that the plants were changed somewhere along the line and it didn't become apparent til many years later. Sort of like sticky shed with tape, worked fine out of the box. I would have preferred they use more of the Siemens caps from that era, but they changed too.

Be careful replacing components, you can do damage to ANY board if proper care is not taken. Spending money on proper tools before hand will save you money on replacement cost in the long run.

Cheers
Alan