Author Topic: E300T lost bias voltage, anybody got the PS schematic?  (Read 199 times)

Offline Oogie Wa Wa

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E300T lost bias voltage, anybody got the PS schematic?
« on: June 15, 2019, 04:37:08 AM »
Hey, long time no.  How have you all been?

I posted how nice my re-tubed E300T sounded a year or so ago.  But, a while back at a campground bar with questionable electrical system it went on the fritz again.  Distorted sound and no volume despite fiddling with the controls.

When i got it home I checked the tube bias, and . . . basically it started out low at about 20mA and quickly drifted down to whatever the actual tube input value from the rest of the circuit was, about 5-7 mA  I'm pretty sure my bias power supply is blown.

This actually happened to me as an infant mortality failure right after I got the amp, and at the time the tech replaced the power supply board and it worked fine for 11 years after that.

Now I'm not so sure he (same dude) can source a board, so I'm thinking he'll want a schematic to work on it.

I do have the regular sound flowpath schematic that was available around here a decade ago, but does anyone have a source for the power supply board?

Thanks, I'd appreciate it.  I miss the tone of the old girl, really loved that amp.  I went to a WTX256 for a spell, but needed more oomph and ended up getting a great deal on an Acoustic Image Chorus that I've been using for a while now.  Nice amp, plenty of power, but an extremely clear signal.  I miss my tube amp coloration and compression, earth-shaking bottom and typical Eden tone characteristics.

The band I'm in now is a great trio, having a blast with 30 scheduled gigs this year, and ever since I got my G&L L2000 30th Anniversary bass when I retired six years ago, I haven't even had any bit of GAS since!!!  That thing was magic going through the E300T, with the AI it's a bit too tweaky for me.

The next thing I'll probably be asking about is how to best prevent power issue damage to amps in general, maybe on one of the other places bass players talk a lot.

Thanks again!
« Last Edit: June 15, 2019, 04:39:48 AM by Oogie Wa Wa »
The Feds Band  -  E300T, WTX-264, Acoustic Image Clarus SL, D115XLT, E210XST, EX112, Fender 250/15; G&L L-2000 30th Anniversary Bass, ESP LTD, defretted Fender  Mexican P-bass Special, Ibanez SRX-300, Peavy Fury 5, Ministar BasStar

Offline Paulinderwick

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Re: E300T lost bias voltage, anybody got the PS schematic?
« Reply #1 on: June 15, 2019, 09:57:59 AM »
Ho Oogie - welcome back - can't help you but Armin will be along soon I'm sure...
UK member, WT330, WTX260, 2 x EX112 (both 4 ohm), WTDI, and a Microtour as well as a Roland Super Cube Bass, Blackstar HT5, Fender Jazz '67, Fretless Fender Jazz '70, Burns Barracuda, Epiphone EB-0, Ashbory, Stagg EUB and guitars and ukuleles and a mandolin as well

Offline Bassmann1968

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Re: E300T lost bias voltage, anybody got the PS schematic?
« Reply #2 on: June 17, 2019, 01:43:36 AM »
Hi Oogie,
he should check voltage from PT1 to PT3.
Check diode D7.
Check voltage over C73 and C74.
Rock on!
Armin

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No schematics available!!! Don't ask for it.
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WTP-Pre,1350,WTX260,WT300/400,WT1000,WTX1000N,NAV,WTDI
D112XLT,D210XST,D410XLT,D810RP,DNS410,DNS112

Offline Oogie Wa Wa

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Re: E300T lost bias voltage, anybody got the PS schematic?
« Reply #3 on: June 18, 2019, 03:33:56 PM »
Aha!!!  Will have him do that!  Thanks as always!!!

It's nice to see things still going on here, I'll make sure to pop in more frequently!

The other good news; got to that same campground Saturday night and lo and behold, six new dual duplex outlets on three separate circuits!!!  Plus the utility changed the tap setting or something on the pole transformer.  Apparently since they put in a few more camp sites over the years and folks motor home A/C units had been having issues, they decided to have it checked out.  Nice!

Thanks again.
The Feds Band  -  E300T, WTX-264, Acoustic Image Clarus SL, D115XLT, E210XST, EX112, Fender 250/15; G&L L-2000 30th Anniversary Bass, ESP LTD, defretted Fender  Mexican P-bass Special, Ibanez SRX-300, Peavy Fury 5, Ministar BasStar

Offline TobiasMan

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Re: E300T lost bias voltage, anybody got the PS schematic?
« Reply #4 on: June 19, 2019, 06:28:12 PM »
Always nice to pull up and see plentiful, clean power.

We were playing at a summer camp a few years go and were having huge problems.  An electrician took a look at things an discovered some blown fuses (antiques!).  They had to shut power off to half the campground during service times, or equipment would malfunction.  Brownouts are not one's equipment's friend!!!
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NXT5 EUB, MTD 535 Fretless, Tobias Killer B-6, 72 Fender Precision
WTX1000N, WP100 Navigator, QSC PL230, WT500, WTDI, Fender Bassman 10
410XLT, 410XST, Generic bin with 2 15" EVs