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Messages - g1

I think there may be some confusion now about the 'distorted sound'.
You are getting the proper sound of the Boss pedal using the FX return?
Quote from: Bandito on April 06, 2024, 04:15:56 PMWould this one work?
That is too low input impedance.  If you want to go with that miniature type, use the AMC2EF2.  In my experience, the miniature type do not sound very good.
If there is not enough room for a 17" tank you can get a 9" type.  For MOD or Accutronics brand, 4EB2C1B is 17", 8EB2C1B or 9EB2c1B are 9" long types.
You may find them for less money at other UK sellers, like Watford valves, etc.
Tubes and Hybrids / Re: Tube Amp Trouble
April 06, 2024, 03:33:18 PM
Sometimes the removal and re-install of tubes will clean up (deoxidize) the sockets.  Maybe that got it working.

Depending on the droning sound, it could be a microphonic tube.  Try tapping them gently one at a time, or holding them with a rag or something to damp the vibration but keep from getting burned.  Generally, microphonic preamp tubes will be higher pitched whistling or squealing, where power tubes will more likely rattle or make low pitched rumbling sounds.
The E to B voltage of T4 (0.3V) seems to not be enough to turn it on.  Maybe checking directly with probes at E and B will give a more accurate reading than checking voltage to ground.
The voltage to turn it on should be developed across R5.  That is created because of current through T1.  What are E,B,C voltages for T1 and T2 ?
Do you have those reversed or is it a typo?  T4 should be the TIP29.
That's not the right schematic for the G.  It's actually for a 1000S (printed on sheet).
100G schematic attached.  Shows 600 ohm impedance for the tank so 4EB2C1B tank should work.
Can you post E,B,C voltages for TR4 and TR6 ?
It is very common for the FM212 (and 65) to develop problems with the differential stage of the power amp (Q9 and Q10), which needs to be well balanced.  That could very well be the cause of your distortion issue, but even if not, it still needs to be dealt with.
Check R83,84,85,86 and replace any that are out of spec.
Replace Q9 and Q10.  This may be tricky as they are no longer made and there will be a lot of fakes available.  Try to get them from a reputable electronic parts supplier, not from Amazon or China.  * edit:  looks like Audiolabs of Georgia has them and they are a legit supplier.
It may be better to find a modern production sub for the 2SC2362K.
Amplifier Discussion / Re: Acoustic 134 reverb
March 23, 2024, 08:09:02 PM
Yes, either will be close enough.  Looks like 8EB2C1A is available.
Amplifier Discussion / Re: Acoustic 134 reverb
March 22, 2024, 06:46:49 PM
Quote from: Pete on March 22, 2024, 05:19:52 PMSooo ... the 4EB2C1B is an interesting suggestion. Can this be mounted either way? – Open side up or open side down?

I don't think they are all that fussy about it, I have seen manufacturers using tanks 'upside down' to what they are supposed to be.  Maybe when they get old and saggy they might start to bottom out.
But if the correct one is available, you might as well get that.
Studio Sound Electronics seems to have them all, including the 4FB series which would be an even better impedance match.  And they have them available in several decay times.
Amplifier Discussion / Re: Acoustic 134 reverb
March 22, 2024, 01:17:02 PM
This listing shows a Gibbs 2 spring unit with about 200 ohms DC resistance at each end.  That would put it in the 4EB or 4FB range of tanks, I think a 4EB2C1B should work.
Amplifier Discussion / Re: Acoustic 134 reverb
March 22, 2024, 11:58:15 AM
Service manual attached.
This one is solid state so I don't think either of those tanks would be correct, but it is possible.
Reverb circuit shown on pdf pg.17
Drive is taken through cap C205 from a 40408 transistor.  Return into a MPSA05.
Amplifier Discussion / Re: Watts vs Volume (db)
March 20, 2024, 08:39:30 PM
Quote from: JonnyDeth on March 20, 2024, 02:56:58 PMWell, looks like I wasted all that time going to college for electrical engineering, thanks for the clarification  ::)
If you can't apply it, I guess you did.
Amplifiers are rated into resistive loads to take reactive power out of the equation. 
Note that I specified amplifiers in my earlier comment to exclude what you said about speakers.

When one walks into a new room, it's best not to have the flamethrower on and start out with the idea that everyone else has it wrong.
Amplifier Discussion / Re: Watts vs Volume (db)
March 20, 2024, 01:41:58 PM
Amplifiers are rated RMS into a resistive load, so VAR is not a factor at the amp side of things.
Yes, sine wave is AC.
Normally we call it a 'signal generator' but it is also an AC voltage generator.  Amplitude and frequency are adjustable.
Function generators may also have other kinds of waveforms like triangle or square, which are alternating but not 'pure' AC.  Pure AC is sine.