Search found 412 matches
- Fri May 10, 2024 1:26 am
- Forum: Technical Discussion
- Topic: Two 20 watt amps in one chassis - layout/grounding
- Replies: 17
- Views: 514
Re: Two 20 watt amps in one chassis - layout/grounding
I’d just build it as a HiFi amp with increased gain and long tailed phase inverters. Use the HiFi approach for the chassis even if you used two power transformers. Crank it up for grit.
- Mon Apr 15, 2024 2:20 am
- Forum: Technical Discussion
- Topic: Output Transformer formula?
- Replies: 13
- Views: 788
Re: Output Transformer formula?
That would be incorrect. For one because your plate dissipation is incorrect. You said a 50 watt amp. And 6L6 isn’t 35 watts dissipation. Plate dissipation for this calculation isn’t about maximum power tube dissipation anyway. That number has nothing to do with how much AC output power an amp with ...
- Sat Apr 06, 2024 11:28 pm
- Forum: Technical Discussion
- Topic: Plexi treble pot does nothing
- Replies: 12
- Views: 549
Re: Plexi treble pot does nothing
Post pictures please and lift the capacitor leg and check that it has the proper capacitance.audiosalvage wrote: ↑Sat Apr 06, 2024 9:00 pm Loop circuit is completely removed from the amp and still no treble control. I checked the pot and all the tonestack wiring. Stumpted
- Wed Apr 03, 2024 2:29 am
- Forum: Technical Discussion
- Topic: Matchless Lightning with EL34 complete Schematic
- Replies: 11
- Views: 816
Re: Matchless Lightning with EL34 complete Schematic
A JTM45 power transformer SHOULD have 350-0-350 and that would get you 440-450 volts DC. They make for a great EL34 transformer. If you’re using cathode bias, you’ll be needing about 35-40 volts cathode voltage and you will subtract that from the B+ for figuring out power output. It still should be ...
- Mon Mar 25, 2024 11:29 am
- Forum: Technical Discussion
- Topic: Fryette Power Station
- Replies: 18
- Views: 1682
Re: Fryette Power Station
I once considered building a similar device in the hopes of saving money. Fact is that I bought a PS100 for $700 and I love it. If I want to sell it I’ll get most of my money back and it’s just to easy to keep it. It allows so much more than just being an attenuator that it’s not feasible to build a...
- Sun Mar 24, 2024 12:03 pm
- Forum: Technical Discussion
- Topic: Heater Wire Ground
- Replies: 30
- Views: 1181
Re: Heater Wire Ground
When winding a transformer the lowest voltage winding sets the ratio of primary to secondary. Yes we want the 6.3 volt and 5.0 volt windings to be 100% correct at loaded output of 5.0 volts and 6.3 volts but the tolerance of the tubes is enough that perfection isn’t critical. My transformers actuall...
- Sat Mar 02, 2024 12:09 pm
- Forum: Technical Discussion
- Topic: Build Ideas for OT with 4.1K Primaries - Cathode biased 6L6s?
- Replies: 5
- Views: 249
Re: Build Ideas for OT with 4.3K Primaries - Cathode biased 6L6s?
I’d test it for impedance ratio. Apply 100 volts AC to the full primary. It should be the blue and brown wires. A simple DC resistance check of the primary should make it obvious which of the three primary wires are the two plates and the center tap. Apply the 100 volts and write down the voltages f...
- Wed Feb 28, 2024 12:20 pm
- Forum: Technical Discussion
- Topic: Sturdy EL34s?
- Replies: 15
- Views: 589
Re: Sturdy EL34s?
I’d put KT90’s in it and forget it. The bias is really close to EL34’s and they are basically the sound of EL34’s in a bigger bottle. KT88’s are also an option but the bias supply has to be modified.
- Sun Feb 25, 2024 1:16 pm
- Forum: Technical Discussion
- Topic: Transformer rescue
- Replies: 6
- Views: 370
Re: Transformer rescue
Thanks for the suggestions. The first suggestion I have is to see if possibly you can pass something very thin between the outer paper insulation wrap and the lamination steel to break the varnish layer between the paper and steel. If that’s possible you then can begin to verify carefully attempt t...
- Thu Feb 22, 2024 2:45 am
- Forum: Technical Discussion
- Topic: imbalance in output tube current - fender deluxe reverb
- Replies: 21
- Views: 575
Re: imbalance in output tube current - fender deluxe reverb
What happens if you swap the 6V6 tubes between the sockets. Watch and record the current again.
- Sun Feb 11, 2024 1:54 am
- Forum: Technical Discussion
- Topic: Removing Negative Feedback
- Replies: 23
- Views: 821
Re: Removing Negative Feedback
And THAT Green wire doesn't go directly to the speaker lead,,, it goes into the tranny first.... I'm good there? thnx a mill~ॐ💃 20240209_001331.jpg Apparently when the transformers were ordered Ampeg specified an internal tap for the NFB which kept the wires closer to the board. It’s actually a goo...
- Thu Feb 01, 2024 12:27 pm
- Forum: Technical Discussion
- Topic: Stable AC Voltages For Testing?
- Replies: 24
- Views: 730
Re: Stable AC Voltages For Testing?
Having a variac is a great thing. I’m going to suggest that you stop worrying so much about input voltage stability while checking voltages though. This is a situation that is pretty much out of your control and I find that while we want precise voltage stability, it’s nearly impossible. I have a de...
- Tue Jan 16, 2024 2:51 am
- Forum: Technical Discussion
- Topic: capacitor values
- Replies: 8
- Views: 2064
Re: capacitor values
F&T makes 80uF that will be better than the Sprague 100uF.
- Sat Jan 13, 2024 7:59 pm
- Forum: Technical Discussion
- Topic: BEST 7189/EL84's To Take Serious Heat.....
- Replies: 6
- Views: 2290
Re: BEST 7189/EL84's To Take Serious Heat.....
Greetings.... I've got some real hot 'n nasty amps that roast power tubes; Mesa, Budda, Vox, & Morgan, and I need a great sounding & heat/voltage handling set of tubes.... I recently read about some Preffered Series 7189's that can handle 400+v, and want to know what else is out there that might al...
- Fri Dec 08, 2023 3:41 am
- Forum: Technical Discussion
- Topic: Just when I thought I had come to understand OT secondaries,,,
- Replies: 25
- Views: 11348
Re: Just when I thought I had come to understand OT secondaries,,,
It’s a lot more revealing to put 100-120 volts on the primary and measure the secondary than such a low voltage like 12 volts. YIKES!!! That could easily lead to death by revealing your susceptibility to heart stoppage by the AC mains. The vast majority of readers on this forum have no training and...