Daddy Dee Posted April 11, 2004 Share Posted April 11, 2004 Often I read threads about finding a tube amp that has been out of service for some time needing to be powered up on a variac. With a few amps lying around, rotated in and out of my main system, but not on a regular basis. I'm wondering how long an amplifier may sit dark before having concern that it would need to be brought up on a variac. Thanks in advance for sharing your take on this question. Quote Link to comment Share on other sites More sharing options...
Deang Posted April 11, 2004 Share Posted April 11, 2004 Dee, don't worry about it. This procedure is for amplifiers that have been sitting for 10 years or more. Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted April 11, 2004 Author Share Posted April 11, 2004 Thanks Dean, Glad to know a few weeks going into months won't hurt. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted April 11, 2004 Share Posted April 11, 2004 Well Dean that is not 100% correct it really depends on if the Electrolyes are new or old even then its better to be safe then sorry. If a piece of gear sits here for more than a few months I bring them up at least slightly slow just to be safe. Craig Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted April 12, 2004 Share Posted April 12, 2004 I read about the importance of slowly bringing up the power to an old tube amp that's been sitting using a variac, so I can understand and appreciate that. But being a tube nube...what the hell is a variac, and what does one look like? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted April 12, 2004 Share Posted April 12, 2004 Its a variable transfomer that are usually about 10" to 12" around with a large dial and a gauge to tell you what voltage your supplying the gear your bringing up. Descent ones can be had for about $100+. I always monitor the current draw as a bring amps up it usually peaks and then falls back slightly to a stable point. This is when I turn it up a little more and repeat until you reach 120V. Craig Quote Link to comment Share on other sites More sharing options...
Randy Taylor Posted April 12, 2004 Share Posted April 12, 2004 I got one on E-bay about 2 years ago for under $30. plus shipping and it was real nice, at that time there were many going for under $50. and many went for under $20. I just did not get that lucky, I guess there isn't that large of a demand for them, but could save you a lot of trouble if you use it on a old tube amp with old caps like Craig said. Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted April 12, 2004 Share Posted April 12, 2004 Thanks for the explaination...I'll have to check eBay later to see if any are still available at a decent price. Although I have old '50s vintage tubes on my new preamp (and will someday on my 300B amp, whenever it decides to get here), my caps are new. Is a variac still required with my rig, or is it really only needed if I owned an EICO or Scott amp? Sounds like it might be a nice thing to have anyway...I do have some old antique tube radios as early as the late '30s, but they've all been restored by my dad, and all their caps replaced beforehand. Quote Link to comment Share on other sites More sharing options...
bkrop Posted April 12, 2004 Share Posted April 12, 2004 Jim, your Dad probably has more than one! (hint hint!) Quote Link to comment Share on other sites More sharing options...
NOSValves Posted April 12, 2004 Share Posted April 12, 2004 Mark, The Variac is just to relieve the gear that has been sitting unused of the slam on the electrolytes to give them a chance to form up. But like you and I both know if you want a true 100% reliable amp they should be replaced with new fresh stock ! Craig Quote Link to comment Share on other sites More sharing options...
artto Posted April 12, 2004 Share Posted April 12, 2004 I learned the hard way. My Luxmans had been in storage a few years. I fired them back up. One by one the power tubes started to let go. Five out of the the six tubes went. At $150 each, used, it was a pretty expensive mistake! To make matters worse, I didn't find out until several years later, when my band was having it's CD mastered at Chicago Mastering Lab, and I mentioned this while talking with the engineer, and he says "Oh yeah. I forgot about that!" "About what?" I said. He says "about re-forming the power supply caps in tubes amps when you haven't used them for a while". At the time I didn't know what he was talking about. But believe me. I sure wasn't going to let that happen again if I could help it! Just use a variac ($50-100 used on Ebay)to be safe. And if you want to add some additional protection, rig yourself up a series wired light bulb to be placed between the amp & the variac. Use a low wattage (10-15W) regular light bulb. When the volatge on the variac finally gets turned up to 100% the bulb should have a dim glow. If it doesn't, you've got problems. In any case the light bulb acts as a current limiter should a cap or something else blow. Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted April 13, 2004 Share Posted April 13, 2004 This is why I love this forum so much...chock-full of useful knowledge and experience from those in-the-know! Thanks... Quote Link to comment Share on other sites More sharing options...
artto Posted April 13, 2004 Share Posted April 13, 2004 One other note: remove the tubes when you're re-forming the caps. When everything is done & checks out ok, shut the amp off, replace the tubes, turn back on normally, & re-bias (if necessary) Quote Link to comment Share on other sites More sharing options...
neo33 Posted April 13, 2004 Share Posted April 13, 2004 "And if you want to add some additional protection, rig yourself up a series wired light bulb to be placed between the amp & the variac. Use a low wattage (10-15W) regular light bulb. When the volatge on the variac finally gets turned up to 100% the bulb should have a dim glow. If it doesn't, you've got problems. In any case the light bulb acts as a current limiter should a cap or something else blow." Thanks for the great tip, Artto. Just brought up two vintage amps last night and one had a couple of P/S caps blown. Though the amp is not damage. Quote Link to comment Share on other sites More sharing options...
tubelover Posted April 13, 2004 Share Posted April 13, 2004 If it blows it blows. Throw it in the trash, get on eBay, and buy something else to give a go round. Quote Link to comment Share on other sites More sharing options...
mark1101 Posted April 13, 2004 Share Posted April 13, 2004 Since I have a couple of lower powered Scotts and have begun looking at the higher powered ones, my philosophy has changed some. I have also gained a little knowledge of the operation of these tube amps. Bottom line, they are pretty easy to troubleshoot and fix, with the exception of some of the intermittent problems. And, most of the important components get changed out in a rebuild, which you most certainly need with any of these old amps. That being said, I look for the "broken" ones, or the ones the seller describes, as "needs work". Again, you need to be careful. But as long as the iron is still good, I have found you can bring them back up to snuff. That is "you guys" can. Bottom line, you don't need to buy the best looking best performing to end up with a really nice sounding unit. The old beat up ones will sound just as good once rebuilt. So you can save a few bucks on the initial purchase to help defray the rebuild costs. I also see many graduating the Scott integrateds to these new fruit flavored separates and custom builds. Nice to know the possible next steps from all the forum pioneers. Quote Link to comment Share on other sites More sharing options...
tubelover Posted April 13, 2004 Share Posted April 13, 2004 This is really, really good information. Thank you for clearing up the old capacitor questions. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted April 13, 2004 Share Posted April 13, 2004 Yup it is becoming painfully clear as the amps keep coming back that not replacing the cans is not in my customer best interest and me for that matter. There is no profit on doing small repair bills when you have to unbox and rebox then take in to the shipper for free. Plus the disatisfaction factor for the customer. Craig Quote Link to comment Share on other sites More sharing options...
artto Posted April 14, 2004 Share Posted April 14, 2004 Ok, then here's a question for you more technically knowledgable electronics guys like Craig & Mark D. How does one determine 'sound wise', if the caps need to be replaced? Or is this something that literally must be measured. I was under the impression that, for instance, noise such as hissing or crackling sounds are indicative of needing the caps replaced. As a comparison, for everyday 'normal use' (which does not necessarily include 'serious listening') I use some little 30 watt Crown D60's. The D60's are about 3 or 4 years older than my Luxman MB3045's. All are well over 25 years old. The Crowns, when the gain is turned all the way up (preamp connected, but muted) have a continuous hissing which is clearly audible anywhere in the room. Yet they 'measure' more than 20dB less noise than the Luxmans on the bench. The Luxmans under the same conditions are virtually inaudible. Yet a number of people have mentioned I should replace the caps in the Luxmans because of their age. Sonically, they beat the Crowns hands down no questions asked. So what's the point in replacing the caps? Quote Link to comment Share on other sites More sharing options...
neo33 Posted April 15, 2004 Share Posted April 15, 2004 " If it blows it blows. Throw it in the trash, get on eBay, and buy something else to give a go round." tubinsoft, you tried EXTRA hard to be controversy and getting people attention, didn't ya? Quote Link to comment Share on other sites More sharing options...
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