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In Reply to: RE: Can I use a 5R4GY in an amp made for 5U4G/5U4GB/U52 ? posted by Frihed89 on June 15, 2014 at 05:21:09
The safe answer is don't do it. The I/P filter cap. limit for a 5R4 is lower than that for a 5U4. Also, the forward drop in a 5R4 is considerably greater than that in a 5U4. A 5R4 drops a whopping 67 V., at the rated 250 mA. of B+ draw.
Simply dropping a 5R4 into a 5U4 "hole" runs the risk of arcing and operating conditions destabilization, due to a B+ rail that's too "short".
Eli D.
Follow Ups:
5R4 MAY be OK, depending on circuit values. Peak current limit is lower for 5R4. Peak current depends on (1)transformer voltage (2) transformer winding resistance plus any other limiting resistance (3) load current (4) value of input capacitor. Voltage drop depends on load, and may not be that different, depending on current draw. Peak current is difficult to measure, but can be modeled using Duncan Amps' free PSU Designer program.
Thanks. That answers the question about the voltage drop.
It's not my amp design.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
This list may help.
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