First the major hum, while I was in there adding the grid stoppers I killed one of the CCS's. My guess is ESD. Thank you Colin for the spares!

Next; back were I started, hum that increases with volume them stops at max. After a bit of pokeing around I found that in my case, the body of the Radio Shzck pot needed to be grounded. Dispite the fact that can find no leakage even with my best meter. Go figure.

Now it is pretty quiet. There is still some hum with volume but considering the amount of gain and the fact I removed the sheilding troble shooting the pot, it will do untill I change to a lower gain tube...John

I thought I had the issue of isolation between the chassis and signal ground resolved, but there is still continuity. I thought the volume pot was the culprit, since I could lift it off the chassis and get infinite reistance. I need to see if a wire strand is causing the problem.

I'm really surprised that ESD killed the 2540 that easily. Mine took a direct hit when checking voltages. Let's just say I about wet myself - didn't shock me, but did get my attention. Do you need a couple of 2540s as spares? I could drop a couple more in the mail if you would like.

Are you going to do the amps next. I'm really excited. This whole process has been much more than I could have imagined......Colin

You'll be pulling a little bit more heater current. Still going to be 12.6, but at 0.6 A instead of 0.5 A. Some tweaking of the R's in filament supply might be needed if you want exactly 12.6. 12-13 ought to be fine IMO...

The 12B4's are mu 6.5 and until you increase heater current or get octal valves, it is the best. Maybe the best without caveats.
regards,
Douglas

ESD is probably what got the fets. with this cold dry air, zap.
the amp was unpluged for a full day PS down to 0 on its own. Fet's are sensitive this is one reason you see zener clamping diodes on some CCS circuts I would like to get another set. let me pay for them this time as you were kind enough to get them.

On the amp front I just converted my JE labs/ FI 300b to WE type 91 and I like it a lot. I have a DRD project in the pipeline. still colecting parts.
I am going to follow along and see. I have some 6a5's I want to use and I want to fool with a transformer phase spliter and parts on hand. But who knows, Dougles is a master of push pull amps and I want to see what kind of transformers are brewing...John

I'll try and get another set on 2540s out to you this week. No need to pay. Your help has been more than enough. Thank you.

What is a DRD?

I'm really nervous about the amps. This preamp was my first serious build using only a schematic. I have more confidence in my abilities, but there is still a lifetime of techniques to learn. I can tell you one thing, I will NEVER build from a kit again. The high I got when Guinevere came to life was worth all the troubles.....Colin

DRD is direct reactance drive, this is the type of amp taht Ron Welborne has. Look here http://www.electra-print.com/circuits.html...John

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