old Ampeg - Hummmmmmmm

Greg_L said:
I'm gonna blaspheme for a moment here about those drums - DW, Gretsch, Tama, Pearl, etc......they're all about the same. If you're comparing apples to apples, a high end Pearl or Tama kit is no better or worse than a high end kit from another manufacturer. Obviously a DW is leaps and bounds better than a Sound Percussion kit, but I did say apples to apples. DW puts together some fantastic kits.....but they can sound just as shitty as cheap stuff. I know a guy with a....sit down for this.....$15,000 DW kit. It's your basic 6pc - one kick, two rack toms, two floor toms, piccolo snare. It looks stunning. Silver sparkle boat-flake finish. It sounds pretty mediocre. Well tuned, good heads, the guy can play, it just sounds like a good drum kit. Not spectacular. Just okay. If you sat in a room with three decent quality kits and someone played them all, you couldn't tell which is which. The area where those high end kits really shine is consistency with bearing edges, quality shells, lug locations, tuning range, and hardware. I think a gigging drummer will be better served with a quality kit. Not so much for the sound, but just for the better fit and finish. For someone that just wants a kit to record, any old decent name brand, good quality kit that's tuned properly with the right heads for the job will be perfect.
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Yeah, that all makes sense and is in keeping with other comments I've read of yours. There's no chance of me buying one of those expensive kits, but I was impressed by the look and finish on many of them.

The yamaha rydeen kit I borrowed for 2 yrs. was bought used there in like new condition for $400.00 with HHs and a ride. That seems like a good deal now. Everything they had yesterday was either super expensive ($800 - several thousand), or an overpriced little kid's set-up.

I guess I thought I could piece together a 22"+ kick, a vintage sounding snare, a pair of HHs and a crash or two out of cheap used gear, but it doesn't seem to work like that. It seems to be a full kit or nothing (although snares are obviously sold separately in huge numbers).

Sorry - I know this isn't the drum forum...
 
heatmiser said:
Yeah, that all makes sense and is in keeping with other comments I've read of yours. There's no chance of me buying one of those expensive kits, but I was impressed by the look and finish on many of them.

The yamaha rydeen kit I borrowed for 2 yrs. was bought used there in like new condition for $400.00 with HHs and a ride. That seems like a good deal now. Everything they had yesterday was either super expensive ($800 - several thousand), or an overpriced little kid's set-up.

I guess I thought I could piece together a 22"+ kick, a vintage sounding snare, a pair of HHs and a crash or two out of cheap used gear, but it doesn't seem to work like that. It seems to be a full kit or nothing (although snares are obviously sold separately in huge numbers).

Sorry - I know this isn't the drum forum...
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Putting one together piecemeal will probably be more expensive and difficult than just buying a complete kit. I don't know about your locale, but in my area complete kits are all over craigslist. The cost of cymbals and hardware alone is a huge chunk of putting a kit together, so buying one complete is probably the better way to go and you can add whatever snare you want later.
 
heatmiser said:
Just dropped off the amp today on a long lunch break.

The dude behind the counter was the same guy that worked on the amp 10 yrs. ago! He recognized his writing on the notes I showed him. He thinks it's probably the filter caps and didn't seem to think it was a big deal. They're also going to convert the 2-prong to 3-prong plug.

He agreed that it was worth fixing as I couldn't get much of a new tube amp for the cost of fixing this one.

They had a bunch of mexi-strats for $399.00 plus a bunch of modified vintage squires for around $300.00 and I was tempted as I need a strat-like guitar.

Then, I walked down the block to the drum store, and holy crap they had some nice kits. DW, Gretsch, etc. All way too pricey...$$$$$$ Damn, those were some fine looking drums! (I don't get out much :o :D).
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What town and what stores were they?
 
It's the same here with Craigslist. Lots of drums. I don't always know what I'm looking at though. I also am reluctant to interract with random Mainers (i.e. "Will trade for firearms or bear meat" or whatever), but that may still be the way to go as there are certainly some low prices out there.

Thanks for the advice Greg. By the time I get my shit together on this what little money I have set aside will be gone!
 
Greg_L said:
Too bad we don't live closer. I have a spare kit I'd let ya use.
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Thanks Greg :).

Another member here nicely offered to sell me their spare kit, but they're not exactly next door either (not as far as TX!).

People here can be so nice. I'm sure I'll figure something out.
 
Holy crap that was fast.

Got a voicemail yesterday letting me know it was ready to go!

I took another long lunch today and picked it up. The work order simply noted that filter cap(s) were bad and were replaced, a 3-prong plug was added (no more electrocutions!)and that the low hum that occurs as the amp first warms up is due to mis matched tubes (which they installed, but whatever!).

Hopefully I'll fire it up tonight and see.

Total bill was about $74.00 including $50 labor. Yay!
 
Cool. You must still be enjoying the 'new' amp because you haven't come back to say if it's good or not!! :D
 
heatmiser said:
....... the low hum that occurs as the amp first warms up is due to mis matched tubes (which they installed, but whatever!).
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Weird. Class A circuit (or trying to be) and mismatched tubes caused a hum that happens as the amp warms up? :confused:

heatmiser said:
Total bill was about $74.00 including $50 labor. Yay!
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Cheap. There wasn't likely a through testing of other caps for that price, and if the main filter went after 50 years, you'd imagine other capacitors may be passed their 'best before' date.
 
Chili said:
Cool. You must still be enjoying the 'new' amp because you haven't come back to say if it's good or not!! :D
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Nah, I tried it for like 5 minutes last night, but forgot that my daughter was having a sleep over. The "studio" is also the guest room, so instead of righteous licks emanating from there, it was whispering and giggling all night. Sounded good for 5 minutes though. Maybe a a little brighter sounding than before...is that possible?

ranjam said:
Weird. Class A circuit (or trying to be) and mismatched tubes caused a hum that happens as the amp warms up? :confused:



Cheap. There wasn't likely a through testing of other caps for that price, and if the main filter went after 50 years, you'd imagine other capacitors may be passed their 'best before' date.
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Yeah, it was so quick and cheap that I don't imagine they went looking for too much in there. You've offered a lot of info, but I'm afraid pretty much all of it is over my head. To be fair to them, I only asked for a specific solution and didn't really ask them to do a thorough exam. I think they sized me up pretty well - just some schlub who wanted his amp to work again.

As for the warm-up hum thing, it's been doing that ever since I've owned it. You turn it on, there's silence for like 5-10 seconds, then a loud-ish hum comes, then it fades away to almost nothing, but remains in the background. I can live with it, but would've been happy if they'd eliminated it too.

They also re-attached the reverb knob that had been loose for years and I'd been unable to secure it.
 
heatmiser said:
As for the warm-up hum thing, it's been doing that ever since I've owned it. You turn it on, there's silence for like 5-10 seconds, then a loud-ish hum comes, then it fades away to almost nothing, but remains in the background. I can live with it, but would've been happy if they'd eliminated it too.
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Ya know, I'd almost think that's normal. I remember some old PA amps my dad used to fix that would do that stuff. Those old amps didn't have delays or output relays that would block the noise until it was ready so you heard it warming up.
 
Chili said:
Ya know, I'd almost think that's normal. I remember some old PA amps my dad used to fix that would do that stuff. Those old amps didn't have delays or output relays that would block the noise until it was ready so you heard it warming up.
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Could be. Like I said, it's always been there. All my electric guitar tracks have had that there in the background and no one has ever commented, "what's that annoying hum?".

Now to address the drum issue and I'm more or less ready to go!
 
I have not come across the 7868 in 50 years! Maybe few made it across The Pond?

Seems a bit of a lost cause and expensive? I would mod such an amp to EL34 I think (but then I have a LOT of EL34s!) .

To produce a LOUD hum at start up and for it never to fade to inaudibilty at say 3 feet those valves must be badly mismatched, to the point I would say that one is on its way out?

I would buy ONE more valve. You would be extremely unlucky for it not to be a better match to one of those in the amp!

Dave.
 
ecc83 said:
I have not come across the 7868 in 50 years! Maybe few made it across The Pond?

Seems a bit of a lost cause and expensive? I would mod such an amp to EL34 I think (but then I have a LOT of EL34s!) .

To produce a LOUD hum at start up and for it never to fade to inaudibilty at say 3 feet those valves must be badly mismatched, to the point I would say that one is on its way out?

I would buy ONE more valve. You would be extremely unlucky for it not to be a better match to one of those in the amp!

Dave.
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Yeah, what he wrote 10 yrs. ago was, "Unfortunately, 7868 output tubes are esoteric, no longer in production, thus very expensive". I think I remember over the phone that he was getting some kind of Russian versions of these ($50 each)?

By "lost cause", do you mean trying to get rid of this start-up hum? If so, that's ok as the lingering noise is pretty low-level.

I don't think the tubes they put in 10 yrs ago would be done after only playing maybe a few hours a week? But I don't really know.
 
heatmiser said:
Nah, I tried it for like 5 minutes last night, but forgot that my daughter was having a sleep over. The "studio" is also the guest room, so instead of righteous licks emanating from there, it was whispering and giggling all night.
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Rock and roll! :D
 
Keep in mind that I am known to do blasphemous and crazy sh*t all the time, since I have no reverence for history. My attitude is that amp would be useless to me as I sit and wait for 7868 tubes to fall in my lap. So, I would spend literally a couple of dollars, and an hour worth of time, and pop in new sockets and rewire those new sockets to accept 6BQ5's. Cheap and plentiful.
Just a side note; a good friend of mine owns an old Marshall Major. Listening to it cranked with a '61 Les Paul/SG I literally pee my pants, but the breeze from the 4 x 15" Marshall cabinet (yep; a 4 x 15") dries them out before anyone knows I've pissed myself. I'm sure this is the sound of God telling me to forsake all other gear. But that amp takes old Genelex KT88's. 'Put in new KT88's' I sez. 'No!' my friend sez. 'Put in 6550's?' I sez. 'NO!' the friend sez. What does he do? Does that eBay thang, and spends $$$$ on used Genelex KT88's. As many as he can find, for spares. :eek: I think he was up to $600 for a spare quad, and another $600 or $700 for the 'main' set of 'not as used' tubes. Crazy. Now 7868's won't be as bad. EH makes a new 7868 that sells for maybe $70 a pair. eBay has used pairs/quads anywhere from $80 up to $175. No thanks. Where's my soldering iron?
 
Definitely replace the main filter caps. You are stressing all of the rest of the circuitry throughout the amp with too much power supply ripple. With tube amps always replace with the same value. Ripple on the power supply raises the average voltage applied to everything. To do the job right you should replace all of the caps 1mfd and above. Whatever you do, do not replace any caps interconnecting stages because it's possible some of them were hand selected to achieve the right tone. If they are not shorted or completely open, don't replace them. High value resistors should be checked for correct value. If they are within 20%, don't replace them. Look for any resistors that have obviously overheated. If any resistors overheated to the point where you cannot determine what the color bands were then you will need a schematic. You should always try to obtain the service manual for any piece of electronics you own especially if you intend to keep it.
 
davegarn said:
Definitely replace the main filter caps. You are stressing all of the rest of the circuitry throughout the amp with too much power supply ripple. With tube amps always replace with the same value. Ripple on the power supply raises the average voltage applied to everything. To do the job right you should replace all of the caps 1mfd and above. Whatever you do, do not replace any caps interconnecting stages because it's possible some of them were hand selected to achieve the right tone. If they are not shorted or completely open, don't replace them. High value resistors should be checked for correct value. If they are within 20%, don't replace them. Look for any resistors that have obviously overheated. If any resistors overheated to the point where you cannot determine what the color bands were then you will need a schematic. You should always try to obtain the service manual for any piece of electronics you own especially if you intend to keep it.
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Yes of course! If there were no ripple at all even badly out of balance valves would not hum!
And yes, do mind the values you fit especially the cap on the rectifier cathode if a valve rectifier. There is a maximum value which depends upon many factors, valve type, AC input voltage and the transformer impedance. The limit for a GZ34 is 60mfds but 50mfds was commonly used as the max. That will be 47mfds nowadays.

Solid state rects are not nearly so fussy but do not go overboard as an overlarge res' cap will do the mains transformer no favours.
Don''t get TOO precious about electrolytic capacitor values. The old types were often +80,-20% in tolerance!

Dave.
 
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