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Old 5th December 2011, 06:24 AM   #1
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Default Bringing up long-stored tube gear

Hello all, I have had in storage for 3 years a McIntosh MC-240, Marantz 8B, Conrad Johnson PV-5, and Scott 350B. I need to wake them up....at last I can set it up again. I once had the system brought up by an engineer who knew tube gear but he is no longer available. I've had the gear 20 years, was in use for many years. All original caps etc. I have a Variac.

I remember the engineer told me it's not just a matter of bringing the voltage up slowly on a Variac, but there is more involved, and that I could blow a tranny if not done right. No tube techs in my small town.

Can any serious technical types give me some advice?

Thanks much,
Jim
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Old 5th December 2011, 08:00 AM   #2
dhaen is offline dhaen  Europe
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Hi Jim,
I think 3 years is hardly any problem but since you have a variac and (it seems) the patience, why not bring it up gently... After all it's all good and valuable kit.
Not sure what your tube-tech meant by there being more to it than a gradual ramp-up. Will be interested what others think...
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Old 5th December 2011, 01:07 PM   #3
DF96 is offline DF96  England
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3 years should be OK. The PSU caps will take a bit more leakage current at first but should settle down. If you hear sizzling switch off and leave the room!
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Old 5th December 2011, 07:40 PM   #4
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I would check the power amp tube bias during the variac power up. This way you can catch a run away bias circut before you blow a tranny, fuse, resister. Aside from caps that could change values, sometimes oxidation can cause an open circut on power tube pins and disrupt the proper bias function.
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Old 5th December 2011, 08:22 PM   #5
tvrgeek is offline tvrgeek  United States
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Brought up a HK Elite 300a that had been stored for 30 years. I had no variac, so I let it have it. Bad noises until the caps started working again. Powers up fine now, but I still plan on re-capping it unless I get a good offer on it. (Original tubes!). I did re-seat the tubes; that is good advice.
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Old 5th December 2011, 08:35 PM   #6
DF96 is offline DF96  England
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You were lucky. Forced 'reforming' of electrolytics is not always as successful as careful slow reforming.
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Old 5th December 2011, 08:39 PM   #7
evanc is offline evanc  United States
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My first decent set was a pair of mc 30s that had been in my father in law's attic for about 30 years. I knew no better and simply hooked them into my system, plugged them in and fired them up. They worked flawlessly from the time I turned them on until about 8 years later when I found out how much they were worth and sold them....

If I were you I would ramp up with the variac and not worry too much.
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Old 5th December 2011, 09:32 PM   #8
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Quote:
Originally Posted by speakerfritz View Post
I would check the power amp tube bias . . . sometimes oxidation can cause an open circut on power tube pins and disrupt the proper bias function.
Would it be a good idea to initially power up with the tubes (at least the power tubes) removed? (Keep the rectifier in place!)

  • Say, zero to about 100 volts on the mains, ramped up over 60 seconds or so.
  • Let it run for 5 - 10 minutes, check the power supply voltages - the intent of the low line voltage is to prevent overvoltage conditions on the unloaded supplies, but if the supply voltages are more than about 15% low, some troubleshooting may be in order.
  • Then ramp back down to zero volts mains input, and install the tubes.
  • Ramp up the mains voltage to full rated value (or even 130V, if your variac has the +5% boost tap) over 30 seconds.
  • Do a quick check for excessive cathode current (a visual scan for glowing plates is probably adequate) and correct if necessary.
  • Let the gear run for an hour or two - applying a little program material is probably in order.
  • Then make whatever factory adjustments are available (cathode idle current, balance, screen voltage, B+, etc).
  • Enjoy it for a few days (warm your hands, keep the tea hot, maybe even listen to some music!) and re-touch the adjustments.
Dale
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Old 5th December 2011, 09:58 PM   #9
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Are you guys serious? 1. Three years is nothing. 2. Gear on OPs list is quality stuff. 3. If it cant handle a simple on-off cycle its not worth a damn.
I mean come on. If we're talking twenty years or more in hot humid storage I'd agree. But three years?
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Old 5th December 2011, 10:50 PM   #10
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Quote:
Originally Posted by SemperFi View Post
Are you guys serious? 1. Three years is nothing. . . .
Some of that gear may have been 40 years old before it went to storage. Even very high-quality gear of that vintage should be given some circumspect TLC.

Dale
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