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Author Topic: Another Studer 827 issue  (Read 2335 times)

cm231805

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Another Studer 827 issue
« on: June 27, 2013, 11:45:53 am »

Hey guys,
 First post here. I've been having some issues with our Studer 827 and in my various searches I noticed there was a lot of good information coming out of here... hopefully I can get in on some of it!

 I was having issues with pops and clicks on our repro head and ended up sending the heads away to ATR Services who were able to remedy the problem which they attributed to a combination of core grounding issues and a bad batch of tape. They were very helpful and got all of the tape replaced.

 So I got the heads back yesterday and put them back on the machine. Upon playing back our MRL, the first 16 channels were looking pretty normal on both the sync and repro head but I noticed there were some problems on the last 8 meters. Channels 17,19,21, and 23 were spiked at +12 and were responding to the MRL recording (the meters were bouncing when the legendary MRL man had something to say). However, channels 18,20,22, and 24 weren't passing any signal. I tried adjusting the REC and SYNC levels in the alignment, but none of the channels responded.

 I've taken the following steps:

 Reseated the heads
 Reseated all cards
 Swapped the preamp card for 9-16 with 17-24
 Swapped the dsub for 9-16 with 17-24 on the head block
 Played back my tone printed work tape to confirm it wasn't just the MRL
 
 I've also played back a brand new blank tape (ATR Magnetics). All meters showed no signal.
 
 I had one one other weird thing happen while troubleshooting this problem. The machine randomly powered down, stayed off for a few seconds and then powered back up.

 Anything jumping out at anyone?

 Thanks so much in advance!
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Timtape

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Re: Another Studer 827 issue
« Reply #1 on: June 28, 2013, 08:05:23 am »

I would recheck that the heads and cards have been seated correctly. It  sounds like something you have done in either removing or replacing the heads and cards.

The fact that the affected channels seem to be grouped together suggests possibly a multi connector not properly contacting at one end. Please note I have no experience with this particular Studer model.

Re the ATR work, it's interesting they implicated both the head and the tapes. If just one of those things, the head core groundings or the tapes, had been at fault one assumes it would have been enough to cause the pops and clicks. The fact that both were implicated seems a little odd. Surely the two factors would have caused two different symptoms. I've never heard of a bad batch of tape causing pops and clicks.

The pops and clicks, plus your mentioning the machine powering down and then up again makes me think of a really stupid question: Is it possible you have a faulty mains connection? That could account for both of those symptoms.

Tim
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cm231805

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Re: Another Studer 827 issue
« Reply #2 on: June 28, 2013, 11:29:12 am »

Thanks for the input. I've reseated the heads a few times now, I thought the same thing but I've rearranged and reseated enough connections to find that it isn't following any one connection. I'm definitely going to give it another once over today.

 The mains connection is fine, always good to double check the dumbest stuff though! I ruled out the pops and clicks being an issue with our machine since ATR was able to recreate the issue on their 827 with our heads and the bad batch of tape as well as their heads and the bad tape. Apparently there was an epidemic of pops and clicks on the repro head with ATR102's last year I think and it ended up being a similar issue with core grounding and the tape. It's not so much that it's bad tape, since it work on some machines, the tolerances of certain machines are lower and higher which can cause the pops and clicks.

 I can't thank ATR enough for their awesome service in dealing with this issue. They got my heads and tape sorted in no time!

 Thanks again!
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cm231805

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Re: Another Studer 827 issue
« Reply #3 on: June 28, 2013, 01:31:55 pm »

Just checked the PSU voltages and they are all within their tolerances...
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Timtape

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Re: Another Studer 827 issue
« Reply #4 on: June 28, 2013, 08:24:43 pm »

OK, if the pops and clicks issue has been fixed, it sounds as if the dropped channels must be a result of something you have done.

 If it's not common to all channels it doesnt sound like a PSU issue.

Tim
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cm231805

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Re: Another Studer 827 issue
« Reply #5 on: June 28, 2013, 09:32:57 pm »

Well I suppose. That said, I haven't done anything since the heads were sent out... all I did was put them back on the machine and the problem started. I think it would be easier to localize because it's only affecting the last 8 channels. Thanks for your help.
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Jim Williams

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Re: Another Studer 827 issue
« Reply #6 on: June 30, 2013, 12:34:56 pm »

Clean the connectors and pins with a non-residue electronic contact cleaner.
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cm231805

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Re: Another Studer 827 issue
« Reply #7 on: July 08, 2013, 01:43:26 pm »

Thanks for the reply, Jim. I've done that on every removable card in the machine as well as all of the DB25's on the head block. From what I've gathered, the issue is after the head block and preamp cards. It does not follow if I swap the preamp cards or he'd block DB25's. It always stays on 17-24.
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Jim Williams

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Re: Another Studer 827 issue
« Reply #8 on: July 09, 2013, 11:16:32 am »

Use a oscillator tone "injection" probe to send a signal from the head connector down to the preamp cards. If you have continuity problems that will show them. It's pretty easy to trace down the signal path with a tone. Where it stops is where the problems lie.

BTW, dump those 1975 vintage RC4559 opamps for some National LME49720NA opamps, you will thank me in the morning.
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