Scott 222C

:dunno: I'm using Sovtek 5AR4's in two Scott 222C's (and a 299A) with no problems whatsoever...

Ask yourself, "What would Herman do?"

Honestly with a 100% restored amp in proper operational condition just buy a 5AR4 from a reputable tube seller (McShane cough McShane) and be done with it! Sometimes I think we all over-think this stuff.

I'm just going on what I've read about new 5AR4s! I'll try a Sovtek, but if I see flashing...

I've read a bit about this McShane fellow... I'll have to reach out and get in touch with him.
 
Honestly with a 100% restored amp in proper operational condition just buy a 5AR4 from a reputable tube seller (McShane cough McShane) and be done with it! Sometimes I think we all over-think this stuff.

I could not have said it better! I would certainly agree with this!
 
Well, bought a Sovtek (MESA Engineering) 5AR4 just now and brought the amp up on the VARIAC--and for the first time I've seen the power indicator come up! I'm very very excited!! I took about 10 minutes of slowing bringing up the supply voltage while keeping an eye on the ammeter, and after I got to 120VAC I left it there for about five minutes to where the ammeter stopped changing and I found that just with the rectifier in, the amp is drawing 0.364A.

I'm so so so so excited to be so close to finishing, but I know I have to go slow or I'll screw something up. Picked up a 33ohm 5W resistor as well today so I still have to drop that in.

I'm leaving home and when I come back on Monday I'll be checking the voltages--excitement!!
 
Well, bought a Sovtek (MESA Engineering) 5AR4 just now and brought the amp up on the VARIAC--and for the first time I've seen the power indicator come up! I'm very very excited!! I took about 10 minutes of slowing bringing up the supply voltage while keeping an eye on the ammeter, and after I got to 120VAC I left it there for about five minutes to where the ammeter stopped changing and I found that just with the rectifier in, the amp is drawing 0.364A.

I'm so so so so excited to be so close to finishing, but I know I have to go slow or I'll screw something up. Picked up a 33ohm 5W resistor as well today so I still have to drop that in.

I'm leaving home and when I come back on Monday I'll be checking the voltages--excitement!!

Excellent!!! Nothing more exciting then when you bring up a piece of gear you poured alot of effort into and to have it work exactly as planned! :yes:

I knew using a modern production 5AR4 wouldn't make your Scott disintegrate into a million pieces like some posts would lead you to believe! :D
 
Yea, there were a couple heart-breaking moments, like when I switched on the VARIAC and turned up the dial slowly to 120V and no current was being drawn at all--then I realized that the amp's switch wasn't on! But then I accidentally slammed the amp with 120V straight on the second try--cut the power as soon as I realized what I did... so, nothing blew up, no arcing, and third try was the charm!

Nerves! This will be the first tube amp I've restored, pretty stoked that it's going so well :)
 
Yea, there were a couple heart-breaking moments, like when I switched on the VARIAC and turned up the dial slowly to 120V and no current was being drawn at all--then I realized that the amp's switch wasn't on! But then I accidentally slammed the amp with 120V straight on the second try--cut the power as soon as I realized what I did... so, nothing blew up, no arcing, and third try was the charm!

Nerves! This will be the first tube amp I've restored, pretty stoked that it's going so well :)

Well I still do not have a variac and have just plugged mine in and hoped for the best. Luckily I've always done it right so far and everything has worked like a charm. I need to quit being so cheap and just pull the plug on one from the bay. It's not like they are expensive!

-Kory
 
Really nice going there Philip. The amp looks great and so does the variac. :thmbsp:
 
Nerves! This will be the first tube amp I've restored, pretty stoked that it's going so well :)

Well, see, there's the deal. It's when you do your second rebuild you'll be all cocky and full of yourself and then something will blow up.

Well, that's how it happens to me, anyway...

Hurry back and put your resistor in. I'm on the edge of my chair here! :yes:
 
Well, I managed to squeeze some basic testing in between coming back home and going to bed--the power supply is totally different from the schematic, so I started sketching out the supply and taking measures wherever a wire ran to a tube pin. And I'm getting voltages as much as 70V higher--for example, the schematic specs 420V to the C/T on the OPT, while I measured 490V. The power resistors were getting very hot, very fast, too--the large white tubular resistor got too hot to touch within five minutes of bringing the amp up to 120V.

I think that this might be because I don't have a full set of test tubes loaded up, though. I'll do up a more detailed, complete, and comprehensive sketch tomorrow and post it.

Quite the head-scratcher... :scratch2:


On that note--would it be too much trouble to ask for voltage readings from the pins of someone else's 222C's 6U8 socket and of a 7189 socket, with only the rectifier in place??
 
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What do you mean when you say you don't have a full set of test tubes?

YOU CAN NOT FIRE UP THE AMP WITHOUT A FULL SET OF TUBES!! Especially if one of the missing tubes is not the rectifier tube. All voltages will be extremely high without output tubes there is just about no load on the power supply.

Beginning of rant

Man I swear every time I read on this site lately I end up with shivers running down my spine.

I keep seeing people post about burned up transformers and gear that worked before they started.... this can all be avoided. Very simple principle should be applied if your not sure what you are doing don't do it.


End of rant.
 
B+ will go down with the insertion of the 7189's. But don't expect it to be as low as the schematic. Line voltages were lower back then.
 
What do you mean when you say you don't have a full set of test tubes?

YOU CAN NOT FIRE UP THE AMP WITHOUT A FULL SET OF TUBES!! Especially if one of the missing tubes is not the rectifier tube. All voltages will be extremely high without output tubes there is just about no load on the power supply.

Beginning of rant

Man I swear every time I read on this site lately I end up with shivers running down my spine.

I keep seeing people post about burned up transformers and gear that worked before they started.... this can all be avoided. Very simple principle should be applied if your not sure what you are doing don't do it.


End of rant.

Thanks Craig--a few posts up I said that this was my first rebuild and it should be noted that this amp did not work before I started, and now it's no longer blowing fuses, so it's a bit of progress! I know I should never run the amp without speakers with all the tubes loaded.

I knew I had to have some kind of load on the supply so I had four throw-away 12AX7 tubes and a set of EL84s loaded in to load down the filament supply somewhat to run some basic tests to make sure I had that side of the supply dialed in correctly (with the 5AR4 out). I took the EL84s out when I put the 5AR4 to run some basic tests.

I've been working on getting some garbage 6U8 tubes and I'll work on tracking down some garbage output tubes for more tests (do they have to be matched?). I won't touch it until then. Thanks for the advice! :thmbsp:


B+ will go down with the insertion of the 7189's. But don't expect it to be as low as the schematic. Line voltages were lower back then.

That's very true, the amp even says 115V on the back. Phew! I'm supposed to be on a break from school, stress, and all that!



I appreciate everyone's knowledge and patience.
 
Sorry for the rant it just gets frustrating. If many of you knew just how many butchered up amps I have to fix you would understand why I get a little emotional about this stuff. It makes the job way less enjoyable and way more expensive for the unsuspecting folks that buy the gear. I've never had the heart to enforce the XX an hour if its stock and XX an hour if you worked on it first policy :banana:
 
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Sorry for the rant it just gets frustrating. If many you knew just how many butchered up amps I have to fix you would understand why I get a little emotional about this stuff. It makes the job way less enjoyable and way more expensive for the unsuspecting folks that buy the gear. I've never had the heart to in force the XX an hour if its stock and XX an hour if you worked on it first policy :banana:

I can understand that--do you think in the mean time I can use 6P14P tubes for testing?
 
I can understand that--do you think in the mean time I can use 6P14P tubes for testing?

Hi,

That's what I 'm using now in my amp and they sound really good,
I switched out a quad of EL84M's just to see how they would sound, now I'll
leave them in. :music: :thmbsp:

Tube
 
I can understand that--do you think in the mean time I can use 6P14P tubes for testing?

Sure they will work just fine. I've been told but have no absolute proof that the 6P14P has close to the same internals as the EL84M. Any EL-84 will work in a 7189 amplifier it just may not last as long as the true 7189. The tubes are completely compatible. The 7189 is just designed to take a higher plate voltage but at a lower total current then the EL84/6BQ5. Both the 7189 and EL84/6BQ5 were rated identical in plate dissipation at 12 watts but at different maximum voltage ratings.

So if an amp has 400V on the plates 7189 it should not exceed 30ma of idle current which equals 12 watts of plate dissipation.

An EL84 with 350V on the plates can have about 34ma of idle plate current which again equals 12 watts of plate dissipation.

When it comes to NOS tubes many old timer type technicians will tell you there is no difference at all between the tubes and the entire thing was a scam...I find that hard to believe myself. Seems like way too many people at way too many companies would of had to have been in on the scam!
 
Alright, for a quick test I tied pin 3 to pin 6 on four 6P15P-EV tubes for testing--I know they're under-rated for use, but I have a good stash of them and figured they would be worthwhile to try as a load in the output section. I also attached a set of speakers to be safe.

Here's my power supply as built. Does anyone recognize it?

2011-01-03-123152_sm.jpg


2011-01-03-132328_sm.jpg


Here's how I rigged up the tube for testing;

 
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Some notes on your photo and comments below

noted photo.jpg



I need to know what the negitive voltage is on the control grid of the output tubes. This would be pin 2. Also do you have a picture of this amps both up top and down below? I need to be sure what version fo the 222C were working with and no the serial number will not tell me only a visual look see.
 
Thanks Craig, I'll rewire up the can cap as you've noted and I'll get those photos up later this evening!
 
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