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studer a80 MKII - VU half inch needs some attention @ love Dynamics Processors (HW)
Old 15th September 2011
  #1
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studer a80 RC-half inch needs some attention @ love

Okay, I've acquired this great machine and the next period I will try to get it up to the needed specs again. while the heads are in fantastic shape the electronics are a bummer ( good price ).
first are the repro and record cards and stabilizer needed to be fixed. I have got a quote on that part of the project from Andreas in Switzerland @ analog - audio
But I'm interested in some other US/UK/EU etc. etc. options to totally rebuild these cards.

cards no are :
1.080.982.12 ( record amp ) 2x
1.080.986.12 ( reprod amp ) 2x
1.080.964.82 ( stabilzer card )
1.080.984.12 ( oscillator ) ( not really needed to be fixed, just checked )


question , can I just use any other same type of card to test/run the machine from let say a normal 1/4 inch A80 ???

and main question, any tips/links to get these cards up to sonic heaven ...
I have a budget for this in the next 3 months planned .. so just making final choices ..

first electronics and then the "motor"parts, but that will be mainly done in the Netherlands.

thnx all in advance
Attached Thumbnails
studer a80 MKII - VU half inch needs some attention @ love-inlinemastering-studer-a80-03.jpg   studer a80 MKII - VU half inch needs some attention @ love-inlinemastering-studer-a80-02.jpg   studer a80 MKII - VU half inch needs some attention @ love-inlinemastering-studer-a80-01.jpg  
Old 15th September 2011
  #2
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Hi Wim,
yes those cards are also used in other A80 machines from the same era.
I have an extra set of those you mentioned I keep as spares. If time permits over the winter period I am planning a recap. Transformers are usually ok. Electrolitics (Frakos) will need to be changed. All the rest should be fine. I guess replacing the tantalums is still an open debate. I tend to leave them on unless specific problems arise. Over the years I have only had an issue with one of the Record amp card and it was a relay. I got it fixed locally for twenty euros (part and labour). The X2 capacitors (line filter caps) definitely need to be changed (I did it earlier this year)


Quote:
Originally Posted by inlinenl View Post
Okay, I've acquired this great machine and the next period I will try to get it up to the needed specs again. while the heads are in fantastic shape the electronics are a bummer ( good price ).
first are the repro and record cards and stabilizer needed to be fixed. I have got a quote on that part of the project from Andreas in Switzerland @ analog - audio
But I'm interested in some other US/UK/EU etc. etc. options to totally rebuild these cards.

cards no are :
1.080.982.12 ( record amp ) 2x
1.080.986.12 ( Reprod amp ) 2x
1.080.964.82 ( stabilzer card )

1.080.984.12 ( oscillator ) ( not really needed to be fixed, just checked )


question , can I just use any other same type of card to test/run the machine from let say a normal 1/4 inch A80 ???

and main question, any tips/links to get these cards up to sonic heaven ...
I have a budget for this in the next 3 months planned .. so just making final choices ..

first electronics and then the "motor"parts, but that will be mainly done in the Netherlands.

thnx all in advance
Old 15th September 2011
  #3
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thnx Riccardo,

I'm really no tech and just want it done by a bizz/guy who has done this / does this for a living ... I have no time and the energy to get to deep into the electronics /soldering ... and I know I would run into frustrations .. I really want to hire a pro ....
let me just polish my ducati ...

man , it's a shame I just can't pop over for your cards :-((

swiss labour is so expensive ...


*** maybe aria electronics would be a great option :-)))))
Old 15th September 2011
  #4
Wim,

I don't know about parts, but if you need a good tech for this,
I sent you a PM with contact info for the owner of E-Sound in Weesp. There is a tech working there who is really a master of all trades and who knows his way around Studers.

regards
Old 15th September 2011
  #5
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^^ present, that would be great / appreciated ...
Old 15th September 2011
  #6
PM sent!
Old 15th September 2011
  #7
Quote:
Originally Posted by inlinenl View Post
Okay, I've acquired this great machine and the next period I will try to get it up to the needed specs again. while the heads are in fantastic shape the electronics are a bummer ( good price ).
first are the repro and record cards and stabilizer needed to be fixed. I have got a quote on that part of the project from Andreas in Switzerland @ analog - audio
But I'm interested in some other US/UK/EU etc. etc. options to totally rebuild these cards.

cards no are :
1.080.982.12 ( record amp ) 2x
1.080.986.12 ( reprod amp ) 2x
1.080.964.82 ( stabilzer card )
1.080.984.12 ( oscillator ) ( not really needed to be fixed, just checked )


question , can I just use any other same type of card to test/run the machine from let say a normal 1/4 inch A80 ???

and main question, any tips/links to get these cards up to sonic heaven ...
I have a budget for this in the next 3 months planned .. so just making final choices ..

first electronics and then the "motor"parts, but that will be mainly done in the Netherlands.

thnx all in advance
Couple of things-
First off your machine is actually an A80 RC MKII. The VU machine is a completely different machine.
The very first thing to do with the machine is replace all the electrolytic capacitors (Most of which will be gold colored Frako) Use the same value or the closest higher value. Also, modern caps are much smaller so you can probably bump up the voltage rating of the cap from the factory to a higher value. Also you should look for low ESR 105 degree replacements from a reputable manufacturer like Nichicon or Panasonic. Don't replace the Tantalum caps. These will probably work as specified till the end of time.
Once this is done then look at the performance of the cards. The cards for a factory 1/2" machine (If memory serves it should be a model RC II VU2/2 or something similar) are not the same as a 1/4" machine. You can put the 1/4" Cards in but they will not perform the same as the 1/2" cards. there are about a half a dozen changes between the 1/4" Cards and the 1/2" Cards.
Typically the only things that have any problems on these cards are the electrolytic caps, the A101 amplifiers (If you have the blue ones and they work, keep them, they are the best sounding) and the relay.
The only change to the circuit I 've made to my machine here is to remove the bias trap (Not needed for playback) and to add a transformerless output.
If you want the best out of the machine, bypass the meter bridge and go directly from the amplifiers. Much cleaner.
Getting the most out of the transport is actually the hardest part. Hopefully your machine still has the large scrape flutter idler. You'll want to send the he******* to someone like John French (I'm sure there is someone of similar skill level in Europe.). a fresh relap and mechanical alignment does wonders.
Next you need to look at the transport to replace faulty bearings and set up the machine for best performance. You'll really need somebody with the correct tools and knowledge to deal with mechanics. These are machines that are built at an extremely high level of precision. Andreas is obviously a good source for service, but I would really search out for the ex Studer factory service people in NL.
All the best,
-mark
Old 15th September 2011
  #8
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hi Wim,

congratulations on your purchase, welcome to the wacky world of analogue tape.

Aside from all the excellent suggestions made here, I would also recommend joining the Studer list, full of old- and new timer analogue tape geeks and techs who can help you keep it running smoothly and troubleshoot any problems from afar.

You'll find it at: STUDER : STUDER

Best of luck. We run a 1/4" machine and use it pretty often for reissues and the like. I considered a 1/2" machine as well, but there's basically no one in the country who uses 1/2", so it would have been a very expensive studio decoration. Good to hear you're doing your part to keep one maintained and running!

Cheers,
Thor
Old 15th September 2011
  #9
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thnx all for your advice and tips ... really great

@ thor, yep keeping the vibe alive, if there are no masteringstudio's handling it ... why would studio's do ... also have a great A80 1/4 ... we will be digging in more to tape I hope ... so even more reason to find local support/relations.
I'm not going to sit and wait until someone sends me a 1/2 inch tape to master :-)) this 1/2 inch will be used for DAW -> 16ch DA and analoge summing to 1/2 inch tape and master directly from there , kind of stem-mastering, summing , sub-mixing .. just following instinct .. and wow .. they look cool
I don't see TAPE coming back to larger commercial facilities, but more to private studio's and INDIE projects where there is a lust and more time for working analogue and a emphasis on quality and tradition.

but if there's a great tech out there I would not mind sending the cards, so still interested in some good options there , but a local tech/relation would be more interesting ( present gave me a good link/pm/tip ) .. you could see the person work :-))) we will see ...
Old 15th September 2011
  #10
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Mine is an RC 1/4" and has exactly the same record and repro cards as Wim's (same numbers)
Despte the 29c degree today I can already see coming rainy winters Sundays recapping all my spare cards heh
Old 16th September 2011
  #11
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^^ and add a nice bottle of single malt ... aaah winter :-)

I made some calls this morning ... I know about the meter-bridge ... would be good to let it go, wonder if there are some similar options like the Aria electronics ... well time to join the studer news-group ...
Old 16th September 2011
  #12
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Don't shotgun the condensers. Those big electrolytics were made with better electrolyte back then. Very often a new batch of Panasonics or Cornell Dublier will have higher ESR than the old Elko / Frako you think needs to be replaced. If the ESR is low and the value is the same, keep it in. You may need to replace, later, so what? but it's not really good advice to fix that which is not broken. Especially with good old Studer tanks. The quality of most passive components made in the past is usually higher, even though the size of modern passive components is usually smaller. In case the machine has been off for a long time, having it run for a while (many hours) may actually repair any borderline condensers as well as automagically relubing the bearings of motors and other moving parts.

Also, the stud mount condensers for the AC filtering (on the back of the machine) are basically unobtainium (except for in huge quantitie$). You will have to manufacture your own stud mounts by cutting off a bolt of the right dimensions and thermal gluing it to the top of a snap in condenser.

Don't do this before first checking the voltages to see if this is indicated.
Again, check the ESR of the condenser in question and if it is near 0 Ohms, fuhgetabowtit.

Check to see if the capstan is polished. If so, it needs to be roughed by someone like Athan (here in U.S.). You say heads are good, so no need to send to JRF. However, he charges a very reasonable fee and can polish them, without relapping, in case that's all they require. He only does least intrusive repairs, as he is a reputable vendor.

Please describe what is wrong with the machine. Why are you determinink the cards not right? You have CCIR daughtercards on repro, or NAB, or spares of each?

Fred Thal of A.T.A.E. is the world expert on Studer tape machines.
The new Studer list is not moderated by him, so you take your chances, over there.

Congratulations on acquisition. We need good stewards of Studers in the world. When you have finished using, please ship to me in States.







Laarsø
Old 16th September 2011
  #13
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Quote:
Originally Posted by Laarsø View Post
Don't shotgun the condensers. Those big electrolytics were made with better electrolyte back then. Very often a new batch of Panasonics or Cornell Dublier will have higher ESR than the old Elko / Frako you think needs to be replaced. If the ESR is low and the value is the same, keep it in. You may need to replace, later, so what? but it's not really good advice to fix that which is not broken. Especially with good old Studer tanks. The quality of most passive components made in the past is usually higher, even though the size of modern passive components is usually smaller. In case the machine has been off for a long time, having it run for a while (many hours) may actually repair any borderline condensers as well as automagically relubing the bearings of motors and other moving parts.

Also, the stud mount condensers for the AC filtering (on the back of the machine) are basically unobtainium (except for in huge quantitie$). You will have to manufacture your own stud mounts by cutting off a bolt of the right dimensions and thermal gluing it to the top of a snap in condenser.
You're completely right.

I have 70's Telefunken M15 and all the capacitors are in top shape. I only replaced that big one near AC plug (is that AC filtering?) which just burned out - probably destroyed by big voltage peak. My techs (guitar tech and pro gear tech) said that equipment which is used frequently does not require change of electrolytics every 10-15 yrs. And that's true, because i've owned vintage Ampeg and Orange amps from early 70s, stock everything except tubes. They do work awesome till this day and capacitor specs are like new.

But I don't think so they were better quality then, in the 70's. They were definietely worse.
Old 16th September 2011
  #14
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Hi Laarso,

no spare cards, so the current ones are the only I have.
the guy who sold it told me he had a problem/hum on the output card ... switching cards .. moved the problem ... therefore I got it cheaper ..

now it just wont record ... ( or I'm just tape-stupid )
I have input on the meters ... the green safe button is on ..
input is pressed , repro is out.

there is sound on the mini-speaker when set to input.

if I press rec & play ..
red lights go on .. tape is moving.
stop
rewind
play ( put meterbridge to repro ) and sadly mmmm notingh hapening.

I have a part on the tape with audio ( seller recorded it ) and it plays , meters moving ???

what's going on ....
just trying to define the machine as it is , what's working or not ....
looks like the record heads dont write anything to tape ... maybe a transport ( car-ride when transporting the A80 ) error .. some loose connector ???

I wish I had some spare/test cards ... working on that :-)
Good bottle of single malt who brings me a set for test ...
Old 16th September 2011
  #15
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it's erasing ... I can remove the audio on the tape ... when I put it in rec mode
Old 16th September 2011
  #16
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Quote:
Originally Posted by inlinenl View Post
it's erasing ... I can remove the audio on the tape ... when I put it in rec mode
That's very good news. I wonder if you could remove the head assembly (the whole block) and put an Ohm meter between the leads on the back of the record head and the multipin connector on the bottom of the head assembly to ensure that the record head is hooked up. It's possible that one of the little lead wires got a cold solder or was inadvertently ripped from its weld.

A flux loop is helpful here, if access to the leads is prohibitive. By taking a coil of magnet wire one can fashion a flux loop and put it against the face of the head to see if a voltage is making it from the alternating magnetic field from the loop (hooked up to an oscillator) and the outputs of the head lead wires on the assembly multipin connector. We aren't looking for response - just continuity.

Good luck troubleshooting. At least it can do submastering, sans layback, for now.




Laarsø
Old 16th September 2011
  #17
Quote:
Originally Posted by Laarsø View Post
Don't shotgun the condensers. Those big electrolytics were made with better electrolyte back then. Very often a new batch of Panasonics or Cornell Dublier will have higher ESR than the old Elko / Frako you think needs to be replaced. If the ESR is low and the value is the same, keep it in. You may need to replace, later, so what? but it's not really good advice to fix that which is not broken. Especially with good old Studer tanks. The quality of most passive components made in the past is usually higher, even though the size of modern passive components is usually smaller.
Laarsø
I found this not to be true. Modern El caps are far more advanced in chemical composition and materials. The specs show it. The new Panasonic FR series are about 1/4th the ESR of tantalums. They are rated up to 10,000 hours at rated tempco's. Leakage current is higher than tantalums, but that's usually not very important except for precision situations and high impedance designs.

Same with opamps, new devices are better. Same with discrete transistors, I replace the BC discrete's all the time in Studers, the noise drops and the tops improve.

When it comes to old electronic components, nostalgia ain't what it used to be.
Old 16th September 2011
  #18
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It's not nostalgia that makes me keep an old component that is tucked away from view once the lid is back on... I realize that it is conventional wisdom to replace the old condenser with new. But conventional wisdom is not always indicated. Just a couple of weeks ago, in my shop, a whole batch of brand new Rubycon 4700 uF 63 V condensers showed higher ESR out of the pouch than the Elko Frako's (gold) from 1978 that I was thinking of shot-gunning just because I could. The capacitance was exactly where it should be on the oldies. The ESR was a good bit lower than in the new. The form factor of the new was too small to work without modification. I'm still not convinced that the new components will outperform an original that isn't broken. Also, it's not only that the condensers which were kept in regular duty may be still robust. In fact, a seemingly tired condenser can repair itself if given a steady drink of current for several hours. If the condenser has broken, is bubbling, is draining, bulging, etc... this would not be good and is a good reason to replace. Also, you don't want there to be shorts when the thing dries out. Otherwise, leave 'em.




Laarsø
Old 18th September 2011
  #19
I'm sorry, but I have to agree with Jim here, virtually any electrolytic capacitor from 1978 is about 15 years beyond its stated lifespan. There are about 4 electrolytics on each card. It is common sense to replace them with modern LOW ESR replacements.
As always YMMV.
All the best,
-mark
Old 20th September 2011
  #20
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studer A80 cards question

Hi Guys,

I have located the problem to a not working repro-card.
it has to be out of the machine to let the other cards work ok and then 'm able to record.

I have attached images of the repro-card and 1 of the record card.
I can get some re-capped A80 cards ( 1/4 inch )
but they just don't have the opening in the cards to let the pin through from the little add-on card .. so I'm a bit worried to get them

is this add-on a special a80 1/2 card .. it's says : NAB 1/2 15"/30"

thnx for any info on it ...
Attached Thumbnails
studer a80 MKII - VU half inch needs some attention @ love-repro_01.jpg   studer a80 MKII - VU half inch needs some attention @ love-repro_02.jpg   studer a80 MKII - VU half inch needs some attention @ love-repro_03.jpg   studer a80 MKII - VU half inch needs some attention @ love-repro_04.jpg   studer a80 MKII - VU half inch needs some attention @ love-repro_05.jpg  

studer a80 MKII - VU half inch needs some attention @ love-repro_06.jpg   studer a80 MKII - VU half inch needs some attention @ love-record_01.jpg  
Old 20th September 2011
  #21
Quote:
Originally Posted by Laarsø View Post
It's not nostalgia that makes me keep an old component that is tucked away from view once the lid is back on... I realize that it is conventional wisdom to replace the old condenser with new. But conventional wisdom is not always indicated. Just a couple of weeks ago, in my shop, a whole batch of brand new Rubycon 4700 uF 63 V condensers showed higher ESR out of the pouch than the Elko Frako's (gold) from 1978 that I was thinking of shot-gunning just because I could. The capacitance was exactly where it should be on the oldies. The ESR was a good bit lower than in the new. The form factor of the new was too small to work without modification. I'm still not convinced that the new components will outperform an original that isn't broken. Also, it's not only that the condensers which were kept in regular duty may be still robust. In fact, a seemingly tired condenser can repair itself if given a steady drink of current for several hours. If the condenser has broken, is bubbling, is draining, bulging, etc... this would not be good and is a good reason to replace. Also, you don't want there to be shorts when the thing dries out. Otherwise, leave 'em.
Laarsø
You need to get some of the new formulations, Rubycon's Z series and Nichicon's HE are good too. I would never use an 85 degree rated cap for replacement unless you want to do it again in a few years. For signal transfer, none are good enough, I must bypass them with quality film caps to overcome their transient damping effects. In some Studers that use bipolar psu's, some of those caps can be removed, permanently. That solves the el cap problem quickly.
Old 20th September 2011
  #22
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Mine are CCIR, I'll have a look. I guess you can swap that "part" depending on what curve you are using?


To Jim
so if I understand correctly you recommend always replacing el caps with 105 degrees ones for almost all applications?
Old 20th September 2011
  #23
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thnx Riccardo, I checked the manuals/pdf .. I know it's a EQ board ( PCB )
I think my cards are the MKII cards while the ones on sale are Mk-I cards ..
I'll consult the person selling which seems to be a knowledge-able person in the UK.

it's interesting to have some spare cards, I can get a complete set ... but still thinking about just sending out my cards to the Swiss ...
Old 20th September 2011
  #24
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Quote:
Originally Posted by inlinenl View Post
thnx Riccardo, I checked the manuals/pdf .. I know it's a EQ board ( PCB )
I think my cards are the MKII cards while the ones on sale are Mk-I cards ..
I'll consult the person selling which seems to be a knowledge-able person in the UK.

it's interesting to have some spare cards, I can get a complete set ... but still thinking about just sending out my cards to the Swiss ...
Andreas comes highly recommended, shoot George (Necola our computer sub-forum Mod a PM) He has Studer connections and knows Andreas.
Old 26th March 2012
  #25
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Quote:
Originally Posted by Riccardo View Post
Hi Wim,
yes those cards are also used in other A80 machines from the same era.
I have an extra set of those you mentioned I keep as spares. If time permits over the winter period I am planning a recap. Transformers are usually ok. Electrolitics (Frakos) will need to be changed. All the rest should be fine. I guess replacing the tantalums is still an open debate. I tend to leave them on unless specific problems arise. Over the years I have only had an issue with one of the Record amp card and it was a relay. I got it fixed locally for twenty euros (part and labour). The X2 capacitors (line filter caps) definitely need to be changed (I did it earlier this year)
Hi and bump to this,

I recently acquired an 1/4" A80 that doesn't record nor put input signal thru the monitor speaker. Mine has no VU-meter panel only speaker with input/repro and channel 1-2 switches. I'm now guessing that the problem lies in the rec amp cards - maybe busted reed relays there? I've already recapped them golden Frakos so most likely they are not causing rec problems.. Playback is fantastic though!

Should I go on and change the reed relays next?


Any help appreciated!

Taneli
Attached Images

Last edited by lbruun; 12th April 2012 at 08:55 AM.. Reason: misinformation
Old 26th March 2012
  #26
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Quote:
Originally Posted by lbruun View Post
Hi and bump to this,

I recently acquired an 1/4" A80 that doesn't record nor put input signal thru the monitor speaker. Mine has no VU-meter panel only speaker with input/repro and channel 1-2 switches. I'm now guessing that the problem lies in the rec amp cards - maybe busted reed relays there? I've already recapped them golden Frakos so most likely they are not causing rec problems.. Playback is fantastic though!

Should I go on and change the reed relays next?

Is this Meder SIL24-1A72-71D suitable drop-in replacement for the Studer's ERNI DILRID-B 1A 1w 24v 72L48 relay?

RELAY, REED, SIL, 24VDC; Coil Voltage VDC Nom:24V; Coil Resistance:2kohm; Switching Current Max:1A; Switching Voltage Max:200V; Contact Configuration:SPST-NO; Relay Mounting:PCB; External Height:7.8mm; External Width:19.8mm; External Depth:5.08mm; SVHC:No SVHC (20-Jun-2011); Coil Voltage Max:30VDC; Contact Configuration:SPST-NO; Contact Current AC Max:1A; Contact Current DC Max:1A; Contact Current Rating:1.25A; Contact Resistance:150mohm; Contact Voltage AC Max:200V; Contact Voltage DC Max:200V; Dielectric Strength VAC:1500VDC; External Length / Height:7.8mm; Mounting Type:PCB; No. of Pins:4; ...

Any help appreciated!

Taneli

It could be different things. Ask your tech to have a look at it.
I had one of the relays you mention replaced two years ago as It wouldn't record on one side.
Old 26th March 2012
  #27
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Quote:
Originally Posted by Jim Williams View Post
You need to get some of the new formulations, Rubycon's Z series and Nichicon's HE are good too. I would never use an 85 degree rated cap for replacement unless you want to do it again in a few years. For signal transfer, none are good enough, I must bypass them with quality film caps to overcome their transient damping effects. In some Studers that use bipolar psu's, some of those caps can be removed, permanently. That solves the el cap problem quickly.
Again, the original Frakos and Elcos in the A 80 R are running fine. They are all rated 85 degrees, just like the ones in the Ampex ATR psu (which also run fine) and, by the way, this is in Centigrade we are talking about, not Fahrenheit - in case someone reads this thread not knowink. Also, these are all in the psu which I am talkink about - not the signal path. In signal path, all is good, too. Love the velvety sound which puts skin on otherwise naked digital recordings. No meter bridge detour in either maschine.

Did you devise a way to stud-mount the replacements you put in? Please explain.


Merçi,
Laarsø
Old 26th March 2012
  #28
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Quote:
Originally Posted by 7038066
I found this not to be true. Modern El caps are far more advanced in chemical composition and materials...
Our research indicates an advance mostly in corner-cutting. Large mil-spec caps are rugged and providink yoeman service. I don't trust new, small form factor and integrity of manufacturers in these tryink times. If it ain't broke...


Quote:
Originally Posted by 7038066
...
Same with opamps, new devices are better. Same with discrete transistors, I replace the BC discrete's all the time in Studers, the noise drops and the tops improve.

When it comes to old electronic components, nostalgia ain't what it used to be.

Can't convince Sterling sound guys of this idea. They don't want the new Sontec op amps. They want the vintage ITI op amps. They like how the depletion zone in the transistor gets vague and fuzzes up the highs after slow cooking for 20 odd years. Slew rate? That's a good way to put it. Speed kills. This is why vinyl and tape sound better than the cleaner and purer digital audio. Good sounds bad. Wrong can sound right.

Cheersø,
Laarsø
Old 26th March 2012
  #29
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Quote:
Originally Posted by Laarsø View Post

Did you devise a way to stud-mount the replacements you put in? Please explain.


Merçi,
Laarsø
Thank you for the replies: Riccardo, Laarsø

I've only recapped 8 x 47uF 40v Frakos on the rec amp cards as they were fluctuating a bit. So far I'm not keen to touch the PSU section as these voltages measure accordingly.

I googled and found out that the red reed relays are common culprit for the A80 input channel faults. Like I mentioned this is new machine for me so it could also be something else that causes input / rec problems. It came from a broadcasting music studio and has seen quite little use (2100h on the running meter).

When I press play and rec the relays are silent so it could indicate that they are busted.. or the card doesn't receive 24vdc or some other component is not right..

Anyways, I need to poke a bit more and test those relays if they work or not..

Any ideas where to look as I'm my 'own' tech here?

Cheers!

Taneli
Attached Files
Old 27th March 2012
  #30
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try removing one of the reprod amp cards ans see if the problem persits ..
if one of the cards is not okay, it will "block" recording ... at least it was @ my 1/2 inch ..
I'm not mistaken .. it was the reprod_amp_card , so NOT the record_amp_card ...

one of the large capacitors on my faulty reprod card was gone .. replaced it and it's running great since ... :-)))

good luck with yours , great machines to have .....
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