Scott 299D Calibration

[A Sound Mind]

Hey there.
I just completed the recapping of a Scott 299D amp and now I need advice to have it tweaked to the best sounding and reliable condition.
I've read several threads on this site and others which detail various procedures and mods, but since I'm rather new to tube audio, most of it was over my head. (I'm a microcircuit designer by trade)

I have the original service manual and they detail basic and advanced alignment procedures. The advanced procedures call for some unfamiliar test equipment such as an attenuator, a vtvm and a 400hz null filter.
Do I really need this stuff and if so, where can I get them and how do I use them?

If you're interested, I installed Russian K40Y and K42Y PIO caps in the audio paths. Bypassing the 'lytic cans, I put in all new electrolytics under the chassis, with the exception of the 4 massive 30uF/500v caps which went behind the front controls. The selenium rectifier was replaced with a solid state bridge. I tested all the tubes on an Eico 667 and replaced any weak or bad ones.
I Deox'd the switches and pots, alcohol cleaned the tube sockets, buffed the chassis, polished the front panel and repainted the transformers. Now it looks like new again. (pics on request)

I slowly powered it up on a variac and heard a motorboated hum on the left channel, but the right channel was pure and clean.

I'll not power it up again without your sage advice.
Thanks in advance!

 

[whaleman]

One thing to keep in mind is to make sure that when you are working on the bench and with no speaker load on the amp, always make sure the speaker switch is off. IIRC, this switch has 2 resistors that provide a load in the off position. Otherwise you risk blowing an output transformer like I did on my 299D.

Not sure the caps in the audio path are electrolytic, but I replaced all audio path caps with Orange Drops. Swap tubes from L-R and see if the noise follows the tubes, if so then you have the answer.

Yes, please post pictures.

 

[A Sound Mind]

Thanks for the hints Whaleman. I'll try the swapping asap.
Yes, I use 16 ohm/50W loads or 8 ohm speakers on the outputs when powering up.
The audio path caps are not electrolytic. They're non-polarized paper in oils that come highly recommended for their superb audio qualities. It can take up to 2 months to get them from Russian federation Ebay sellers, but they can't be beat for their price and performance.
I'm still looking for guidance on how to calibrate this amp and the necessary test equipment. I've uploaded some pics.....

 

[A Sound Mind]

Well, I ran the amp and attempted to calibrate it per the manual, but I think it has some other serious problems:
1. Both channels work, but the right channel is extremely weak.
2. The left channel doesn't appear to have as much power as it should either.
3. There's a serious hum with the scratch filter off.
4. The overall sound quality isn't as good as expected. I recently recapped a Scott 222A and it sounded a heck of a lot clearer.

Please tell me if this creates a problem; I broke off one of the lugs on the 1M balance pot. This lug was directly opposite the other three. I believe this lug is common with the wiper, so I moved the connections to the center lug. I haven't been able to locate an exact replacement.

I inspected the entire amp for shorts and cold solder joints, plus I retested all the tubes and came up with nothing.
No components are running excessively hot.

You can reference my earlier photos in this thread, or I can upload pics of a specific area.

 

[whaleman]

That broken pot should be ruled out before you continue looking elsewhere...

PM also sent.

That is one nice unit, appears to be an early model 299D. Thanks for the photos.

 

[A Sound Mind]

Agreed. Reasearching futher, the broken lug is not common with any other lug. It's a fixed center tap and connects to the loudness control. If I can't find a replacement, I hear that a voltage divider can be installed in its place. Can someone help me on that?