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Messages - mandu

The reverb level is at the output of the first amplifier after the reverb output.
Pull out the reverb tank inputs and see if the hum exists.
If no, the drive to the tank is the culprit.
If yes, pull out the output from reverb tank and see if the hum exists.
If yes, the first amp after the tank output need to be checked.
If no, see if there are any other transformer nearby.
The tank will make hum if kept nearer to other transformers.

FET to mute power amp during powerup???
Did you try to connect the preamp output to another amp?
Or from another audio source to the power amp input?

The picture you posted shows common cathode (connected to the -ve).
The other two are for red or green (or yellow if you power both) goes to the +ve
The limiting resistor may be 1 if wired on the cathode or 2 nos. if wired from anodes.
Quote from: saturated on September 07, 2023, 02:58:08 PMyes sir just looked it up....

there is a schematic for the inside...transistors...diodes...zeners...resistors...
but thats cool i had wondered if some transistors are simply called voltage the one we put in my Peavey Audition Chorus because they have three legs and look like transistors.
so the answer is

Your reply is funny.
The Newcomer's Forum / Re: MarkBass/Class D amplifiers
October 09, 2023, 07:58:10 AM
Disconnect the SMPS and power the amp with regular transformer power supply.
The problem could be elsewhere.
Have you heard the Yamaha G100 amps? The preamp and speakers are part of the sound.

A comparison of the 3 models...

The Newcomer's Forum / Re: Shorted IEC line filter
January 28, 2023, 06:40:50 AM
These line filters live for many years.
Probably, the ac supply voltage exceeded more than the rating of some component for too long.

Amplifier Discussion / Re: Fender 112 Deluxe Plus
September 01, 2022, 10:40:08 AM
The diodes may be producing some RF induced hum. Try connecting 0.01 uF capacitors across each of the diodes to see if it reduces the hum.
An interview with Bob Galien by sweetwater where he explains some designs of his amlifiers.
(30 minutes)
For those interested.


One schematic with 3886 output with +/- 31 volts supply has 130 ohms in the PSU circuit.
The other schematic with 2050 output with +/- 22 volts supply has 10 ohms in PSU circuit
No mention about the output power in both the schematics.

Is this the resistor attached to the 12 volt regulators?
Quote from: Tassieviking on June 19, 2022, 08:58:36 AMThanks guys for the answers, I think I will not keep the Electrolytic caps since I don't know the age of them.
Better be safe then sorry.

I would suggest you experiment with those old electrolytic capacitors before throwing out to learn something and acquire some knowledge out of it. Regards.
I had a pair of new 6800mf/80 volts caps in shelf for 10 years. With capacitance meter both measured good above 6800 mf. To clear doubt I connected a 40 volts DC supply and left for 30 minutes. The capacitors became very hot and I have to throw them away.
Either the capacitor becomes dry (lower capacitance) or have lower dielectrics (high leakage current).
You can connect a DC power supply to it and check if they survive as I did.
If the physical look is bulged, then throw them away.
Can you check if C7 (2.2 mF) in poweramp is OK?