T-REX Squeezer schematic or info for repair...

[nothingMaker]

Hi.

My Squeezer has stopped working.
The transistor near the small transformer, identified by BF51***, is explosed damaging also the capacitors.

I'd like to repair. Anyone have a schematic? Or known the transistor model?
I need to known the model of the transitor.

Which other parts could be crashed with the problem?

Thank you so much

[klampfenfreak]

Hi.

My Squeezer has stopped working.
The transistor near the small transformer, identified by BF51***, is explosed damaging also the capacitors.

I'd like to repair. Anyone have a schematic? Or known the transistor model?
I need to known the model of the transitor.

Which other parts could be crashed with the problem?

Thank you so much

Did you get this information? Same Problem, the element near the xformer is burned completely and melted with the transformer. Can't read the type of the element anymore.
Thank you for your help

[J M Fahey]

Very much doubt anybody has the schematic.

The amp has a tube, yet runs from 12V DC and eats only 250 mA (of which 150 mA is for filaments alone) , so I guess the small transformer and transistor you mention is some DC-DC converter to get high voltage ... and the transistor might have exploded.

Write straight to T-Rex and then post here what they answer.

Without a schematc we canīt be of much help

[mozwell]

enjoy

The BC639 transistor is rated 0.5A 80V, i guess that unless you have a short on the HVDC line, some switching spikes have killed the transistor.
i would add 2x 33V 1W zeners from the collector of the transistor to 0V to absorb any spikes

[oc disorder]

Thanks to Apollo Music & Free Stomp Boxes Org its a BC639.... SMD components mainly

[J M Fahey]

Weird Marketing plot mixed with a couple errors.

1) the worst: the input FET in no way can work like that; it shows unbiased floating gate and its drain goes to only 4.1V and through 1M?
No way.
The Gate must use that 1M resistor for biasing, the drain must go straight to 9V (not shown).

2) the circuit itself is a datasheet application for the excellent THAT analog processor, here wired as a compressor, no tube magic at all but very good SS technology.
Of course, that does not sell, so they added an unneccessary 12AX7 (of which they waste 1 triode) just to claim tubeyness.

The "warm fat tube sound" really comes from the bass enhancing multiple feedback filter at the end of the pedal, just before the tube.

3) who needs +240V to work.
So they made a switching converter,which must have worked well on Protoboard, but which lacks safety measures.

As Mozwell suggests , some peak transient limiting is needed.
I would go as far as using just *one* 33V zener, go figure, because that bridge rectified secondary shows me that it's not a flyback converter (which would use just 1 diode) so there should be no large spikes on the primary ... except by poor design .

Besides I'd add an upward pointing plain diode (1N4002) from BC639 collector to ground, to avoid it being reverse biased, which is very stressing.

Although the Zener(s) can fill that function, if used (recommended).

4) Given the actual circuit inside that pedal, they might have used the tube just as an expensive pilot lamp, with filaments engaged for that warm orange glow ... and not much else

[MarkusBass]

The schematic was drawn by a member of freestompboxes. He reverse engeneered the effect from the PC board. He made several mistakes - some of them are described on the forum in further posts while other are not. With the input FET it's clear that the gate should be connected to 4.1V through 1Meg resistor. But what is here important is the power supply part which seems to be drawn correctly.

Mark

[klampfenfreak]

enjoy

The BC639 transistor is rated 0.5A 80V, i guess that unless you have a short on the HVDC line, some switching spikes have killed the transistor.
i would add 2x 33V 1W zeners from the collector of the transistor to 0V to absorb any spikes

Thanks for that hint. Would you draw a scheme of that zeners addition, please? 0V means GND?

[apollomusicservice]

Last year I wrote about this compressor on FB forum, there are two corrections R52 to gate of Q2 and missed C32. Here is schematic.

[J M Fahey]

Thanks for taking the incredibly boring and stressing work of tracing and posting a complex pedal

[MarkusBass]

I still see some mistakes on the schematic. For example, the output tube V1A has no anode resistor. Also the R9 output resistor seems to be too small. And the LEVEL pot is connected incorrectly (and its value is too small). Great work but some adjustments are still needed. Do you have the compressor and the correction is possible?

Mark

[J M Fahey]

I also fell for the same

The load/plate resistor is drawn close to the HV PSU and is made out of 3 x 15K resistors ... a reasonable value.

R15 will work , as is, although if so it kills both gain and output level.

Maybe it's a drawing error and maybe it is that way, I already said that I find that triode stage after the real modern compressor more of a cosmetic value than something else.

Maybe otherwise stage gain was excessive and it used to overdrive the next stage, which after all is a guitar preamp input, expecting guital level signals (say 100mV RMS, not 50X that).

Boutique pedals often amaze me by their crudeness and/or conceptual errors

Another clue to the "Photoshop Design style" , meaning cut and paste from "somewhere else" are the protection diodes D5 and D6, which must have been in "the other" circuit (datsaheet?/app. note?/commercial compressor?)
They must be used at the actual input, to protect from gross overloads (say Junior connected the speaker out of another amp there), so they really should be at Q2 input.
Maybe there's others.

[mozwell]

Hi Klampen, to add the surge suppression zeners I would do it like this
2x 33V 1W zeners in series
cathode of zener #1 to BC639 collector
anode of zener #1 to cathode of zener #2
anode of zener #2 to emitter of BC639

Even if you add this, as there is no current limiting on the power supply, its just a forward converter, any short or high current on the secondary will kill the primary switching transistor BC639.
Check the 4 diodes on the secondary of the transformer & (with power off) check C3 & C4 for shorts....

[MarkusBass]

I also fell for the same
The load/plate resistor is drawn close to the HV PSU and is made out of 3 x 15K resistors ... a reasonable value.
R15 will work , as is, although if so it kills both gain and output level.
Maybe it's a drawing error and maybe it is that way, I already said that I find that triode stage after the real modern compressor more of a cosmetic value than something else.
Maybe otherwise stage gain was excessive and it used to overdrive the next stage, which after all is a guitar preamp input, expecting guital level signals (say 100mV RMS, not 50X that).

My mistake. I also noticed (too late) 3 resistors in the power supply. But isn't 45k too small value for 12AX7 (especially with 10k on the output)? Maybe they wanted to decrease the gain of the tube stage.

Mark

[apollomusicservice]

Once again checked the schematic is correct, I do not have the pedal just photos.
In diagram anode resistor is not an error, but is composed of R6, R7 and R8,
then R9 has a value which is drawn, how as a Level pot which is correctly drawn as its value.
I also checked the protective diodes D5 and D6 are in that position.
Adjustment are certainly necessary, but it would no longer be this device.