Trace Elliot Bipolar Bear transistor upgrade?

[glebert]

Picked up a non-working Trace 4001 amp (GP12 SMX preamp and 280W power amp) for next to nothing. The Bipolar Bear board is not working, looks like a fair number of shorted output/driver transistors, which are TIP35C/36C and TIP31C/32C respectively. Based on previous thread about my Eden WT300 (http://music-electronics-forum.com/t46412/), which is similar voltage rails (+/-70 volts at least), I'm wondering if one of the problems with these modules is the 100V Vce rating on the TIP transistors. The Trace does not have any clever biasing tricks like the Eden does (that I can tell) and at full output the Vce will be close to 140V at the peaks on the non-conducting side of the push-pull.

Trace Elliot GP7 150-300watt SM.pdf

Should I consider replacing TIP31C/32C transistors with MJE15030/31 as Juan suggested in the Eden thread (see guys, I do listen sometimes ), and what would be a good higher current transistor to sub for the TIP35C/36C?

Thanks in advance,
Greg

[J M Fahey]

Picked up a non-working Trace 4001 amp (GP12 SMX preamp and 280W power amp) for next to nothing. The Bipolar Bear board is not working, looks like a fair number of shorted output/driver transistors, which are TIP35C/36C and TIP31C/32C respectively. Based on previous thread about my Eden WT300 (http://music-electronics-forum.com/t46412/), which is similar voltage rails (+/-70 volts at least), I'm wondering if one of the problems with these modules is the 100V Vce rating on the TIP transistors.

Please actually measure rail voltages and post them here.
IF you have the 300W board which should indeed have 65-70V rails, TIP35/36 have NO business there.
Probably some lazy Tech just read the schematic but not the *Notes* which as Enzo says: "are there for something".

Personally I have always been disappointed by TIP35/36 ; look great on paper (100V 25A 125W dissipation) but are sissies out in the field.
After minutely rereading their datasheets many times, I noticed (hidden in plain sight ) that their SOAR rating is appalling ... and THAT is what kills bipolar transistors when driving complex loads such as ..... um ...... speakers.
I would use TWO pairs in the 150W amp, not one as optimistically stated in schematic, I guess around 45V rails.

The 300W one, with higher voltage rails, uses 2SC4468 and 2SA1695 , as mentioned in the NB service notes nobody reads

That design is old (80 something?) so that particular pair might be obsolete/unavailable but then lots of modern types are available.
JUst meet 140Vce, 10A and 100W dissipation in TO247 case and youŽll be fine.

The Trace does not have any clever biasing tricks like the Eden does (that I can tell) and at full output the Vce will be close to 140V at the peaks on the non-conducting side of the push-pull.

Trace Elliot GP7 150-300watt SM.pdf

Should I consider replacing TIP31C/32C transistors with MJE15030/31 as Juan suggested in the Eden thread (see guys, I do listen sometimes ), and what would be a good higher current transistor to sub for the TIP35C/36C?

Thanks in advance,
Greg

[glebert]

The 300W one, with higher voltage rails, uses 2SC4468 and 2SA1695 , as mentioned in the NB service notes nobody reads

Will post rail voltages when I get a chance to measure (but it is AC going to the Bipolar Bear, so will probably need to pull failed devices to verify DC rails), but you are right that the outputs for this should be the 2S4468 and 2SA1695 (haven't taken the heatsinks off yet). I am really shocked that they put the TIP numbers in the schematic and then change that in the notes. That would never have flown at the companies I worked for.

[Enzo]

A quick look at the safe operating area map of any power transistor will show that those 250v 16A transistors are good for one or the other, but not both.

[soundmasterg]

I've got a Trace Elliot GP7 SM150 with blown transistors. I was going to sub in the other types mentioned in the notes but didn't get around to it yet. Noticed you're in portland glebert...I'm in the area also. we appear to have the same first name too...haha.

Greg

[glebert]

First one to get theirs working wins!

[soundmasterg]

It will probably be you as I'm in the middle of searching for work and fixing a car. Amp is sitting on a shelf until I'm done with those other tasks unfortunately.

Greg

[glebert]

You don't know how slow I am and how many projects I have stacked up. Literally. Stacked up.

[soundmasterg]

You don't know how slow I am and how many projects I have stacked up. Literally. Stacked up.

The same applies to me, but in addition to amps, it is pedals, guitars, basses, and cars!

Greg