I looked at the datasheets comparing the 6973 and 7189A. Max plate & screen voltages are similar. 6973 draws less heater current (450mA).
...
Announcement
Collapse
No announcement yet.
Search Result
Collapse
500 results in 0.1776 seconds.
Keywords
Members
Tags
-
Last edited by Rhodesplyr; 08-08-2020, 03:41 AM.
- Likes 2
-
Evolution of the 6973 tube
Many popular output tubes have a development history, like how the 6L6 eventually led to the 7581A, I know the story of how the EL84 became the 7189 and then...
-
The historical fact is that some manufacturers, even back in the golden age of tube electronics, kept manufacturing costs down by using transformers that...
- Likes 1
Leave a comment:
-
My take from personal experience having played around with Dynaco amps for years and having rebuilt two pairs of Dynaco MkIIIs with improved driver boards...
Leave a comment:
-
That's how it's done in transistor combo organs, but Hammond's mechanical tonewheel generator is locked to the AC mains frequency with a synchronous motor,...Last edited by Rhodesplyr; 05-24-2020, 09:45 PM.
Leave a comment:
-
True, but as you said in your post, leakage is less likely to be the culprit here....
Leave a comment:
-
Electrolytic caps can have a number of different things wrong with them. DC leakage at working voltage is only one of them.
It's possible for...
Leave a comment:
-
Many thanks for posting all the photos! It's a big help.
I also mounted an IEC socket. This one had had mice in it and required a lot of corrosion-related...
Leave a comment:
-
Magnatone M15A Reverb Tank Mounting?
I'm ready to finish a long Magnatone M15A restoration, and I need to mount the new spring tank in the cabinet. This is a cabinet with an angled baffle between...
-
I think the problem with the LED idea is that the neon lamp is not just the light source for the LDR as it is in the Fender circuit. It's also the LFO. There's...
Leave a comment:
-
Magnatone M15A Echo click
I've been slowly working on a bit of a basket-case Magnatone M15A, and I've now got most of it sorted out. The most obvious issue remaining is an annoying...
-
The other rule of capacitors is that you hear their effects far more if their value places them in the middle of the audio frequencies you're listening to....
Leave a comment:
-
I like this explanation, including taking UL operation into consideration. A huge proportion of the circuitry of this amp goes into Magnatone's complex stereo...
Leave a comment:
-
What's the design purpose of hybrid fixed/cathode bias?
I've been slowly working on a bit of a basket-case Magnatone M15A, so I've become very familiar with the circuit.
It uses a 2 x 7189A push-pull...
-
Yes, NP0/C0G types are the best ceramic types in terms of being closest to being ideal capacitors. They are extremely stable with respect to temperature and...Last edited by Rhodesplyr; 04-03-2020, 03:11 PM.
Leave a comment:
-
Conclusion: Flipping the PT around to hang underneath the steel chassis drops the hum from 11mV to 5mV, which is acceptable for an amp like this.
...Last edited by Rhodesplyr; 03-21-2020, 04:36 PM.
Leave a comment:
-
I'm pretty sure it's being picked up in the tone control section. I tried pivoting the transformer on all its axes. No significant difference. What looks...
Leave a comment:
-
Sometimes you need to post about something for the solution to come to you.
I realized I hadn't tried moving the power transformer, so I unbolted...
Leave a comment:
-
Gibson G30 solid-state amp hum
I've been working on a 1972 Gibson G30 SS amp, and the hum (60Hz) at the speaker is 11mV, not affected by any of the controls, including the volume control....
Leave a comment: