Bias and plate voltage measurements.....

[JeffreyC]

Hehehe, this is fun - 2 brand new matched pairs of Winged C's from Antique Electronic Suppy -

Pair 1
Milliamps - 77.6, 84.4 Plate voltage - 468, 468

Pair 2
Milliamps - 66.9, 67.3 Plate voltage - 478, 477

Bummer, I was looking forward to these being close to where they should be.

Anyone care to help me with installing the bias circuit??? Pics of one installed in a DR504?

[OldSchoolDave]

Will these be on the new items section of the VHR site?

Once all the planets align, yes .

Dave

[JeffreyC]

Anyone care to comment on the Winged C measurements? I thought maybe it would
surprise some of you....maybe I should have purchased from somewhere else?

Also - question about my master Volume pot....I've noticed that I don't get much increase in volume
until quite a bit past the halfway mark...probably 2/3 on. So, there seems to be a small range on the pot
from a good useable band vol level and cranked. It's not a problem really, but I'm curious as to why this may
be. My Reeves Custom 50 is a much louder amp, but it's currently set at an ideal bias point. Could this just
be the current bias setting on my Hiwatt? Thoughts?

Gosh this place moves slow....

[OldSchoolDave]

Anyone care to comment on the Winged C measurements?

Pair 2 seems sufficiently matched. Pair 1, not so much. And, the two Pairs aren't in the same range. Did you order a matched quad or two matched pairs (there's a difference)? AES is a reputable firm. It would surprise me if they shipped a matched quad like that. Have you contacted them with your findings?

FWIW, I've also had good luck with TheTubeStore.

Also - question about my master Volume pot....I've noticed that I don't get much increase in volume
until quite a bit past the halfway mark...probably 2/3 on. So, there seems to be a small range on the pot
from a good useable band vol level and cranked.

Does that pot appear to be original? I've got one DR103 that behaves completely opposite - it maxes out very early in the sweep. Other Hiwatts I have come on more predictably.

Dave

[JeffreyC]

Pair 2 seems sufficiently matched. Pair 1, not so much. And, the two Pairs aren't in the same range. Did you order a matched quad or two matched pairs (there's a difference)? AES is a reputable firm. It would surprise me if they shipped a matched quad like that. Have you contacted them with your findings?

FWIW, I've also had good luck with TheTubeStore.

Thanks Dave. No, I have not contacted them yet, but I will. I bought two matched pairs....I guess the most surprising thing is that everyone recommends the Winged C's as new production tubes that most have had luck with in vintage Hiwatts without biasing. These are way too hot. I purchased two pairs hoping that I'd at least get lucky with one.

Does that pot appear to be original? I've got one DR103 that behaves completely opposite - it maxes out very early in the sweep. Other Hiwatts I have come on more predictably.

When I bought the amp from Jarrett, the master vol pot had already been replaced with a cheap one from Mexico. I bought the nice PEC pot from the VHR site
and installed it myself. Both of these replacement pots act(ed) pretty much the same though.

[JeffreyC]

Hey guys, thought I'd provide an update on this....could not wait for the VHR mod as I need this amp to be my
backup for gigging.

I took my amp to Bruce at Mission Amps to do the bias mod. He did a nice non-invasive job.

I tried the two pairs of Winged C's last night. I was able to bias one pair with bias pot turned all the way down,
but the other pair still could not handle the voltage - still redplating. My guess is that the production method of the Winged C's has
changed and so I would caution anyone thinking they could run these tubes in a vintage Hiwatt.

[OldSchoolDave]

I tried the two pairs of Winged C's last night. I was able to bias one pair with bias pot turned all the way down,
but the other pair still could not handle the voltage - still redplating. My guess is that the production method of the Winged C's has
changed and so I would caution anyone thinking they could run these tubes in a vintage Hiwatt.

Did you swap inner and outer pairs? If so, did the redplating follow the tubes or stay with the sockets?

Dave

[JeffreyC]

This is for DR504 - no inner/outer pairs.

I bought matched pairs from Antique Electronic Supply. One pair biased in around 35ma and is running fine. I got the other pair
down to around 46 ma at the lowest possible bias setting on the trim pot and so they were still red plating. The pair that I was able to
bias at 35 was also at the lowest possible setting on the trim pot.

For comparison, when first swapping in the Winged C's in place of NOS Teslas (which were properly biased by Bruce), Winged C's started around 78-80 ma, so I do have quite a range of adjustment with the bias trim pot. So from what I can tell, the Winged C's just don't seem to be up to the task.

[OldSchoolDave]

This is for DR504 - no inner/outer pairs.

DOH! Sorry 'bout that.

So from what I can tell, the Winged C's just don't seem to be up to the task.

That's an interesting discovery, as the =C='s have a pretty good reputation, until now. Might this spike activity in a whole new market for "NOS" Modern Production tubes ?

Dave

P.S. On a related note, I see that AES is now offering "broken-in / tested" JJ E34L's. I imagine that's in response to an unacceptable DOA rate.

[JeffreyC]

Might this spike activity in a whole new market for "NOS" Modern Production tubes ?

Dave

P.S. On a related note, I see that AES is now offering "broken-in / tested" JJ E34L's. I imagine that's in response to an unacceptable DOA rate.

Gosh, I hope so!! Would be nice since the NOS market really seems to be drying up.

[mhuss]

Were these factory matched, or matched by AES?

Note that each manufacturers' EL34s seem to require a different bias voltage -- sometimes several volts different -- to produce a given idle current at a given plate voltage. (This is why adjustable bias is not really an "option" any more, IMO). I find even the same manufacturer/different lot sometime varies a bit. This is for *all* tubes currently manufactured.

--mark

[JeffreyC]

Thanks Mark. Yeah, what you're saying makes total sense to me. I believe these were probably matched by AES, but don't know for sure.