Need help troubleshooting HM2 kit gone bad

[antonis]

Would it even work at all if it had been the other way around?

In theory, there shouldn't be any issue 'cause for discrete JFETs Drain & Source are fully interchangeable..
(but, unfortunatelly, no manufacturer produces a D-G-S device..)

[amaurythewarrior]

ok, false hope then.

So checking transistors with an ohmmeter, is that reliable? with 2 pairs of legs that should conduct only one way, and the third one none?

I was doing that on T1 and after reading I see mosfet are tested differently? Because S to D was conductive both ways.

[antonis]

It is reliable in the degree of a dead-alive transistor..

But, as long as it concerns your particular circuit, only T2 might got dead due to B-E junction reverse voltage applied..

You can test it utilizing two diode model (B-C & B-E)

[PRR]

> how to check transistors with an ohmmeter. ...I didn't get the same pattern on T1 (k30a) ....realized it doesn't say EBC but SGD

There are two (many!) kinds of transistors.

Pins EBC is a "Bipolar Junction Transistor".

Pins SGD is a "Junction Field Effect Transistor" or "Metal Oxide Field Effect Transistor".

There are also UJTs, PUJTs, MESFETs, HEMTs, FREDFETs, OFETs, DNAFETs, IGBTs, and stranger things.

[amaurythewarrior]

> how to check transistors with an ohmmeter. ...I didn't get the same pattern on T1 (k30a) ....realized it doesn't say EBC but SGD

There are two (many!) kinds of transistors.

Pins EBC is a "Bipolar Junction Transistor".

Pins SGD is a "Junction Field Effect Transistor" or "Metal Oxide Field Effect Transistor".

There are also UJTs, PUJTs, MESFETs, HEMTs, FREDFETs, OFETs, DNAFETs, IGBTs, and stranger things.

hmf. Do they all test different ways?

[amaurythewarrior]

It is reliable in the degree of a dead-alive transistor..

But, as long as it concerns your particular circuit, only T2 might got dead due to B-E junction reverse voltage applied..

You can test it utilizing two diode model (B-C & B-E)

okay, well I've test it and both pairs are conductive one way and not the other. If I understood right, this is the expected behaviour for a diode. So, supposedly I can assume it is functional? (From what I read and understood, if they are damaged it is pretty obvious when testing)

And again, thank you guys for the help, this is much appreciated.

[antonis]

well I've test it and both pairs are conductive one way and not the other. If I understood right, this is the expected behaviour for a diode. So, supposedly I can assume it is functional?

At a first glance, yes..!!

P.S.
You didn't mention anything about Collector-Emitter measurement..

[amaurythewarrior]

Ah, I've mentioned it, or let's say "implied" it, without the proper terminology, so I'm not surprized you did not understand my explanation.

Collector to emitter, non conductive both ways.
I was a bit confused by a page that seemed to say the contrary, but I compared with a different transistor which behaved the same, so I deduce it should be correct.

So basically at this point I can test roughly all of the components I think except maybe the ICs: diodes, resistance, caps, transistors... I'll do that when I rebuild it.

[amaurythewarrior]

So I feel kinda stupid... Turns out it was the battery after all. I tried a brand new battery from the store (not a never used one lying around for years) and it seems to work well. I don't know to what extent but apparently good.

There is some noise with a power supply, not with the battery, but I wonder if it's just the PSU itself that's responsible, I know some cheaper ones can cause problems.
I can get the high pitched noise again... Which turns out to be feedback from the insane amount of gain the pedal, has... So this was apparently a combination of that and low battery, but I did not expect feedback at low volume since I never use distortion pedals...

I've filmed the whole building process and recording a demo I'll post later.

But at least I did not really waste my time, because that pushed me to learn a lot of things that will be most helpful in the future, so thank you to all those who contributed!

[antonis]

>I can get the high pitched noise again... Which turns out to be feedback from the insane amount of gain the pedal, has...<

Try to raise C8 value up to 100pF, say..

As for PS noise, a simple RC LPF might substantially impove noise reduction..