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Author Topic: STUDER A810 tape transport: problem solved!  (Read 16316 times)

Offline yjwu

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STUDER A810 tape transport: problem solved!
« on: June 13, 2011, 07:21:07 PM »
Dear Reel to reel experts:

After replacing five RC4559N's on reel motor control board, my STUDER A810 starts playing music!! (I had not found which of these IC's were fault yet. Listen this A810 singing is a much more joyful moment!

I would like to thank Ki Choi for sharing experience in pinpoint the problems. Followed his suggestion
I replaced most of the electrolytic capacitors on basis board, and many more. It will extend the life of this A810 for another period. He also suggested me to review the checksum value of the firmware chips. Before I call my friend for help I did the  IC swapping. Surprisingly problem had been solved! Maybe those chips are still O.K. I will defer the check until audio/mechanical line up are done.

Thank you for taking time viewing my post. I want to thank Mac for sharing his experience of fixing his A810.

Wish we all have healthy A810 to enjoy. Let the legend continue forever!

Best Regards,

Y.-J. Wu

Offline Ki Choi

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Re: STUDER A810 tape transport: problem solved!
« Reply #1 on: June 14, 2011, 10:26:42 AM »
It is always nice to have a happy ending to any saga.  Good job, YJ.

I am impressed that you were able to find the problem without having access to the other working parts for quick swaps.  It's a good experience for you and hope you too have gained a huge appreciation for Studer's design team as I have in making the A810 so much easier to work on in comparison to other consumer machines and even the Otaris.

As long as your A810 is going through the power up routine with some counter number display first, the firmware version display (2591), VU meter lamp resets and finally locking in the capstan motor phase-lock-loop indicatior (if you have your capstan control board configured to do so - otherwise when you lift one of the tension arms or have tape loaded) without any EEEXX display, your firmware chips are healthy and good.  There's no need to look any further on the firmware checksums.

Now that you have a working machine, you need to call DocB and sign up for The Tape Project!  ;-) You won't know how good the A810 really can sound until you have threaded the Arnold's Overture tape and hit play.

Although I get wrapped up in hoarding machines but they are just one of the means to the ultimate end - good music.
Ki Choi

Offline yjwu

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Re: STUDER A810 tape transport: problem solved!
« Reply #2 on: June 16, 2011, 10:10:02 PM »
Hello Ki:

Yes. This machine waits for good tapes to be played on. Just be curious: for the "out of print" tape project TP-006 (Oistrakh played Scottish Fantasia by Max Bruch) is there any schedule for reissuing?
Although my A810 was back to life (from near 20 year's dormant, perhaps?) it still suffered "EEEE01" error from time to time. I found that the problem was the EPROM IC No. 10. Its pin 28 was rotted and easily broken off. I tried my best to solder the little pin back to its "trace" pedestal.
My first try did not last too long. The difficult part is that the soldered joint did not have enough mechanical strength to withstand insertion into socket. The weak electrical contact would not survive thermal cycling neither.
On my second try I placed the "amputee" chip in socket first and then do the soldering work. It seemed to last longer.
This morning it still gave the notorious "EEEE01" error. Restart the machine again it stays on till 7:00AM when I have to go to work.
I think I still have to visit my friend and have EPROM's content retrieved (with good checksum value). Then migrates the code to a set of new 2764's. BTW, I had not check the recording function yet. Tape winding is also on a slow side. As I disassembled this A810 before the transportation (reel motors, both tension arms, pressure roller assembly and tape lifter, head block, capstan motor rotor and shaft were packed to a small carry on luggage) all those mechanical alignments has to be checked again. Three screws to lock the reel motor do have a lot of play to find tune the breaking. I do not have tension gauge. I adjust the position of brake band and reel motors until a different forward/backward torque was experienced on both reel axes. It was rough estimation. Too busy. Some bugs may still lurking around!
When this A810 was powered up, before "2591" display, I can hear the "thump" from the monitor speaker. As far as I know all Studer-ReVox machines has relay to block the output from switch on surge? I will find the circuit diagram later.
I am lucky to be able to trail the steps from pioneer like you and many reel to reel "先行者" (Chinese, sorry). It is great to be part of this society!


Thank you again and hello from the other part of the globe.

Y.-J. Wu

BTW: I vewed a Youtube clip by Richardu47 on your place. Wow! It is heaven of reel to reel tape recorder! (I got circuit boards set of his ReVox C270 a year ago.)

Offline yjwu

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Re: STUDER A810 tape transport: problem solved!
« Reply #3 on: June 16, 2011, 10:33:11 PM »
Hello Ki:

I forgot to mentioned that when I got time to play my A810 I was curious to see how many of those 5 RC4559N's were bad. A quick way is to plug-in those chips, one by one, onto A810's tension board. (Each has one RC4559N)
I was shocked to know that all of them function correctly on A810's tension board! Then why this machine suffered so long with tape transport problem? Before the swapping of RC4559's, this A810 could not even play tape. Press "Y" resulted in the lighting of the corresponding LED and "Fast Rewinding". Is that only bad contact? (At swapping I also changed four 100uF capacitors on reel control board. Two of them were O.K. Other two only measured at 75uF)

So that is the magic spell!

Best Regards,

Y.-J. Wu

Offline Ki Choi

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Re: STUDER A810 tape transport: problem solved!
« Reply #4 on: June 17, 2011, 10:17:26 PM »
Hi YJ:

I trust DocB will chime in with the answer on the Tape Project tape availability.

If your EPROM had contacted with the battery acid enough to eat into the pin, my guess is that you would need to replace the EPROM socket as well.  Before you replace the EPROM socket, I would suggest you use a little DeOxit on the pins and socket contact points.  Ultimately, it is better to replace the socket.  I had done the same to one of my A810s' MPU card.

Judging from your email address, you must be in Taiwan.  I travel to Taipei about once a year for work.  If you have the means to burn an EPROM chip, I can send you the BIN file for the IC10 via email.  Otherwise, send me your mailing address. I will put the IC10 for 2591 version in the mail to you.

The thump sound you hear as well as the VU meter jump full scale after power up initialization is common on old A810s.  It is due to some of the 5532 OPAMPs in Line Amp card needing replacing or I have also found both Rerp Amp and Line Amp card with marginal electrolytic capacitors making noise after power up.

Lastly, did you replace the two electrolytic caps in the head preamplifier located under the headstack for +/- 15V supply?

Ki
Ki Choi

Offline docb

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Re: STUDER A810 tape transport: problem solved!
« Reply #5 on: June 18, 2011, 12:32:29 PM »
Our license has expired for TP-005 and TP-006 and at this time we have no plans to renew those licenses.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline tonykyma

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Re: STUDER A810 tape transport: problem solved!
« Reply #6 on: June 19, 2011, 07:25:21 AM »
Hi YJ
I believe that you are a DIYER and analog lover, I just fixed a B62 which was damaged in shipping of not working in control section, lucky it is designed in all mechanical relays that in my limited knowledge still can be fixed , A810 sound not bad but it like a digital machine more than analog , too many IC in used ,I did modification for my A810 with change the out put section into TUBE out put this came out in very positive return ( whatsbestforum.com) next step is the repro head in put section too, analog music with today's TUBE amp is the best combination I do believe !
cheers
tony ma

Offline yjwu

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Re: STUDER A810 tape transport: problem solved!
« Reply #7 on: June 19, 2011, 07:14:43 PM »
Hello DocB:

Thank you for your information. I will look forward to join the tape projects to testify the charm of reel to reel format.

Best Regards,

Y.-J. Wu

Offline yjwu

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Re: STUDER A810 tape transport: problem solved!
« Reply #8 on: June 19, 2011, 07:26:32 PM »
Hello Tony:

It is great to hear from you that there are more possibilities of A810 tweaking. I will visit the link later. I had seen people doing a modification to have a direct head output (balance XLR) from A810. Quite impressive.
Maybe it is my next step.

Congratulations on your B62 project. Maybe it has already bring sweet analog sound!

Best Regards,

Y.-J. Wu

Offline mithamo

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Re: STUDER A810 tape transport: problem solved!
« Reply #9 on: September 26, 2011, 11:38:57 PM »
Hello DocB.

Thank you for the information appreciated.
Mithamo says Hi.