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|9th April 2009, 09:06 PM||#1|
Join Date: Dec 2002
Location: Ontario, Canada
Studer A-80 Record amplifier relay
A couple of years ago I purchased a very nice Studer A-80/RC 1/4" stereo master recorder.
Now, in the time I have owned it I have been using it strictly as a playback deck.
Yesterday I decided I wanted to archive some upcoming live radio broadcasts, so I went about buidling up a set of RCA-XLR cables and tried my hand at a few test recordings.
Everything went very well, except for the fact that nothing was being recorded on one channel.
"Oh no...not the record head!", I thought.
Then I tried something simple, the beauty of which comes with a professional deck like this: I swapped the left and right channel record amplifier cards. Bingo! Now the channel with nothing being recorded moved with the card.
So at least I was able to focus on the record amp card and stop worrying about a head problem!
After studying the schematic and considering what could be causing the problem, I focused on a small daughter card containing a couple of transistors, diodes, a cap and a relay. The purpose of this card is to connect the line input signal (after EQ and amplification) to the record head via the relay once the deck is put into record mode.
After checking all the parts I found that the relay is bad...the coil is open and an applied voltage does nothing!
To perform a quick test I soldered a jumper connecting the pads that would normally be connected by the relay.
After putting the card back into the machine everything works correctly.
Now, after that lengthy intro, a few questions:
Is it a bad idea to jumper across this relay and keep the signal going to the record head at all times, noting that there is no bias applied to the record head until the deck is put into record mode? I'm sure that it's not a good idea, as Studer would not have added this relay circuit were it not necessary.
Next question is where to find a suitable relay for this type of application?
I am sure that the original (ERNI DILRID-B 1A 1W 24V, DPDT, DIP 14 package) is impossible to find and my searching on google has not even turned up a datasheet!
Obviously the relay needs to be of VERY high quality as the input signal passes through it to the record head.
I'm not beyond mounting a new relay off board as DIP 14 replacements seem to be very scarce, but what are the best types for audio signal use?
Many thanks for any suggestions!
|16th June 2009, 10:12 AM||#2|
Join Date: May 2008
Relays in DIL packages often are Reed-types. Since yours is broken anyway, you could open it up and look, what is inside.
If it is a Reed type, replace it with one. If it is not, look for small signal relays, e. g. Omron's G6K or G5V series.
Did you ask Revox for a spare part?
If you've always done it like that, then it's probably wrong. (Henry Ford)
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