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Old 31st October 2010, 06:38 AM   #21
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Quote:
Originally Posted by taj View Post
Wave, you mean these? I've got some too. The photo doesn't do justice to their 'pinkness'.

Exactly, Todd!
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Old 31st October 2010, 12:56 PM   #22
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Originally Posted by vinylkid58 View Post
Is there any reason why you need two 5U4's? With one rectifier, you would need to replace fewer caps.

jeff
It's the way the amp was designed. I don't have any idea about tube amp design, but my father thought it was overkill to have two 5U4's also, drawing about a full amp combined, at least for home audio use. And I'm not concerned about having to replace six caps that will only cost around 15 bucks or so.

Keep in mind though that this amp was designed and used in a Baldwin electronic organ and was used for both the manuals and pedal stops, so the amp had to be rather robust to fill a small to medium sized church. Even with efficient speakers, 23-28 watts doesn't go all that far when you're trying to fill a large area like that with a full range of frequencies, especially those pedal notes.
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Old 31st October 2010, 03:31 PM   #23
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Glad your back on path to having your amp up and running.


Good advice a page back, Make it your decision!
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Old 31st October 2010, 04:47 PM   #24
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Your loud 'ticking and popping' sounds could be a bad solder connection or broken lead.

If you can do it safely, considering the lethal voltage everywhere, I would suggest turning the amp upside down (make sure it's stable), power it up with a crappy test speaker connected, turn the volume up a little, then tap the leads of all the components and all solder connections with something long and non-conductive, like a chopstick. This will expose any bad solder joints or broken leads.

[edit] another thought: clean the tube pins and socket holes somehow too, it might be a bad contact there. Spraying some Caig DeOxIt (sp?) will help. I'm not sure how to clean the socket holes other than spraying them. Maybe insert a small drill bit and scratch it around a bit.

..Todd

Last edited by taj; 31st October 2010 at 04:56 PM.
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Old 5th November 2010, 12:19 PM   #25
chops is offline chops  United States
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Wow, it's been a crazy busy time these past few days, hence my absence here.

At any rate, I ordered the new electrolytics Tuesday and got them in yesterday, bought a new heavy duty "long" toggle switch to replace the little cheap power switch that was installed by the other guy, and thoroughly inspected the every connection head to toe on the amp when i had the chance.

Today I will be installing the new caps and switch and then powering it up!
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Old 5th November 2010, 07:22 PM   #26
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Got everything installed and now playing. There's zero hum or hiss. It's dead silent in that regard, however...

It sounds fine when there's music playing, but whether the gains are all the way up or down, there's a faint "sizzle" sound coming from the speakers, mostly from the tweeters. The sizzle is independent of each channel also. It almost sounds like the surface noise of a record.

Could this just be the new caps (burning in) or something? Could it possibly be the old original coupling caps going? Anybody ever witnessed this type of noise before?

I'll post up some pictures later tonight when I get some spare time.

And many thanks in advance for any info you guys can provide me!
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Old 5th November 2010, 09:05 PM   #27
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Could this just be the new caps (burning in) or something?
I've never heard new caps make any noise.

Any old carbon resistors in the PS?

jeff
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Old 5th November 2010, 09:31 PM   #28
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Well I shut the amp back down, switched the 5751 tubes from left to right just to see if that had any effect on the problem and it now seems that the noise is completely gone! That was over an hour ago and it's still running nice and silent. I guess it was just a dirty contact or something.

Anyway, here's some pics from today...

Click the image to open in full size.

Click the image to open in full size.

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Old 5th November 2010, 09:44 PM   #29
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It seems like the sizzling was a 5751 tube socket pin connection. That makes perfect sense.

..Todd
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Old 6th November 2010, 06:08 PM   #30
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Originally Posted by taj View Post
It seems like the sizzling was a 5751 tube socket pin connection. That makes perfect sense.

..Todd
Well no, I don't think it does actually. I'm beginning to think it's either one of the 5751 tubes or one of the 6L6's that might be a little flaky. Within the first hour and a half or so of operation from being completely cold, this sizzling sound occurs. It sometimes sounds like air leaking from a tire but not constant. It varies in intensity and duration.

If I lightly tap the 5751 of the channel in which is making this sound, you can hear the tap effect the sizzle. Same holds true if you tap either of the 6L6's in that same channel.

The thing is, my brother rolled the tubes in this amp shortly after getting it. He thinks he knows what he's looking for when buying old NOS tubes off of eBay, but he doesn't. He figures if the tubes are a well known name and the seller says they measure good, then they have to be good. This obviously isn't the case as the seller often doesn't test the tubes properly or doesn't test them at all.

Furthermore, he had two other similar issues with his 300B amp after he started rolling the tubes in it, the last of which ultimately killed the amp. IIRC, half way through a CD he was playing, one of the 300B tubes started glowing bright cherry red. There's no telling how long the tube was running like that until he noticed it. Of course, when he did notice it, he shut the amp down immediately. Ever since then, no matter what tubes he tried in it, that channel was dead and I think the 300B in that channel wouldn't even heat up anymore.

So in short, what I'm trying to get at is that I have really no clue as to how good these tubes in this amp really are. They all measure great and are very closely matched to each other, even the two 5U4's. I also don't know what the 6L6's are brand-wise. There's no markings on them anywhere. All I know is that the 5U4GB's are GE and the 5751's are RCA.

I think I'm going to completely re-tube the amp as even the 5U4's make a little "jingling" sound of their own when you put your ear down close to them. Actually, you can hear them jingling when sitting on the floor in front of the amp.

Have any of you guys ever witnessed tubes that measured good but had issues while listening to them? What was the cause?

Again, many thanks in advance!
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