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by VintageJon
Fri Nov 18, 2005 4:03 am
Forum: Technical
Topic: Tube Advice
Replies: 13
Views: 3219

Hello?

-Jon
by VintageJon
Fri Nov 18, 2005 4:02 am
Forum: Technical
Topic: Tube bias-- this has been posted before but...
Replies: 7
Views: 2043

Same rule still applies:

Cathode current - Screen Current X Plate voltage = IPD.
Should not exceed 17W as this is 70% of the 25W Max Plate Dissipation for an EL34.

-Jon
by VintageJon
Fri Nov 18, 2005 3:57 am
Forum: Technical
Topic: Differences between EL34 and 6CA7?
Replies: 8
Views: 2538

Should also have mentioned the filament current current difference.
MUCH more filament current is required for an EL34 and it's relatives than for a 6L6GC.

-Jon
by VintageJon
Fri Nov 18, 2005 3:33 am
Forum: Technical
Topic: Tube bias-- this has been posted before but...
Replies: 7
Views: 2043

OOPS! 50 not 30.
sorry!
-Jon
by VintageJon
Thu Nov 17, 2005 4:24 am
Forum: Technical
Topic: Tube bias-- this has been posted before but...
Replies: 7
Views: 2043

I have retubed a number of 30W CAthode Biased Orange amps and have not had to rebias one of them!!!! You MUST measure and calculate Screen current and subtract it from the Cathode current or it looks pretty scary as MAX Plate Dissipation for an EL84 is 12W. I think you're OK just going with a MATCHE...
by VintageJon
Wed Nov 16, 2005 5:18 am
Forum: Technical
Topic: PPC 212 ohm's query
Replies: 3
Views: 1202

If you have a 8 Ohm interal load and a 16 Ohm external load and they a3e in parallel then your total load would be 5.33 Ohms. I wouldn't do it!

R1 X R2 / R1 + R2 = Rt in parallel...

-Jon
by VintageJon
Wed Nov 16, 2005 5:14 am
Forum: Technical
Topic: Amp hum normal?
Replies: 30
Views: 15897

Well, your hum is the power amp or power supply.

Check all filter caps and connections. Power tubes good?

-Jon
by VintageJon
Wed Nov 16, 2005 4:25 am
Forum: Technical
Topic: 70's tubes used in Orange
Replies: 7
Views: 1995

Also recall Mullards in the original in the 60's/70's examples I've seen and can remember...

-Jon
by VintageJon
Wed Nov 16, 2005 4:21 am
Forum: Technical
Topic: Differences between EL34 and 6CA7?
Replies: 8
Views: 2538

Kannibul: actually the EL34/6CA7 is a "kinkless tetrode" while the 6L6 is a "beam power pentode". Note that the surpressor grid is connected to the cathode INTERNALLY in a 6L6 while the surpressor grid is floated and connected to pin 1 in the EL34 and 6CA7. In a 6L6 the surpressor is a beam-focus-pa...
by VintageJon
Wed Nov 16, 2005 4:07 am
Forum: Technical
Topic: Transfomers I can't find... Not the Robot kind
Replies: 24
Views: 5665

Mercury or Orange. Any good 100W will do it...

-Jon
by VintageJon
Wed Nov 16, 2005 4:05 am
Forum: Technical
Topic: horrible buzzing/crackling on rockerverb reverb
Replies: 9
Views: 2396

Damn fine advice from timboardman...

-Jon
by VintageJon
Wed Nov 16, 2005 4:04 am
Forum: Technical
Topic: horrible buzzing/crackling on rockerverb reverb
Replies: 9
Views: 2396

Nay,
I think's it's a connection issue...


-Jon
by VintageJon
Wed Nov 16, 2005 4:01 am
Forum: Technical
Topic: Tube Advice
Replies: 13
Views: 3219

Another thought, 12AY7 or perhaps 12AT7 for pre-amp stage would help.
In fact, I'd recommend 12AT7 for phase inverter. Better current drive and much less harsh than 12AX7...

-Jon
by VintageJon
Wed Nov 16, 2005 3:42 am
Forum: Technical
Topic: Questions for some tube experts out there...
Replies: 29
Views: 7173

Yeah let that cat be and find a Pro. Are you in or near Austin Tx???

"I bought the cab empty and loaded it with 8 ohm speakers..."
DId you wire them series/parallel? It could be 8 or 32 or 2 Ohms depending on how you wired it...

Did you Ohm-it-out???

-Jon
by VintageJon
Wed Nov 16, 2005 2:46 am
Forum: Technical
Topic: Channel Switching Problems - An experiment
Replies: 4
Views: 2000

Nuetrik is made to the Switchcraft length-standard. Many Oriental knock-offs are not. I've seen this too...

-Jon

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