Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: chocopower on April 10, 2012, 09:48:57 am
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Hi guys,
I have a AB165 bassman with really low screen grid voltages (220v). Poping noises and other weird noises.
Choke measure 2M3 with my DMM.
I install a 1k resistors as a "choke" and voltages get back to usual 450-480.
I think is obvious that choke is semi-broken, but, what could cause the damage???
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A connecting lead wire may be "hanging by a thread". The winding itself may be partially melted or broken. Somewhere, there's a partial break of continuity which is causing resistance to skyrocket. If you can get inside a bit, you may be able to see if a lead is partially disconnected.
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The 2M3 measurement was once the choke was out of the amp?
You can possibly fix it, if the break is not buried inside the winding. I fixed the B+ winding of the PT for a VTVM that was like this. Once you open up the choke, you'll probably find the wires coming out of it are soldered to much finer wire inside. If you carefully remove a few turns, you may find where the break occurred, and be able to resolder the winding to the lead-out.
If you were gonna trash the choke, and lived in the US, I'd say send it to me! Only cause I'd find a use for it... :icon_biggrin:
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It will sound cool without the choke anyway,so don't fret.Traynor amps often had no chokes and they sound killer good.
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You get more shimmery glass in tone using a resistor instead of a choke. Sometimes great and other times you need to use a choke to smooth out an amp a bit
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Thanks everybody!
I´m gonna open it and check the external turns.
I already have here an old technical (84) who rewind trafos for very few €. (sorry HotBluePlates, i´m in Spain).
Last time i paid 40€ for rewind an Orange OD 120 output trafo, so, that choke don´t should cost more that 25€.