Ceriatone DZ30 (Matchless HC30 clone) Crackle

[psychic fuzz]

Hey all,

Just recently purchased a used Ceriatone DZ30 Matchless HC30 clone and a couple issues have popped up.

1) Starting to get a crackle from input 1 of the EF86 channel. Sometimes it happens while I'm playing and other times it happens if I unplug the cable from jack while "on".
2) Output level will sometimes get quiet then back to normal, I'm assuming this caused by the same issue. This has also happened on input 2 of Ef86

It sounds like tube issues but I've put all new tubes in. Which tube should I start with? Any other insight is greatly appreciated, thanks!

[Stevem]

It could be any number of things .

For starters.

Does the issue take place right away, or does the amp have to warm up some ? If it uses carbon Comp resistors then one of the plate load resistors might be going south.

If one is going bad then you might as well shot gun it and replace all the plate load resistors in the preamp and PI section.

Have you had the amp open yet ? It might have had some mod's done to it and or parts replaced and there's a poor solder connection now due to that.

[bcmatt]

My first amp I built was that amp kit and I still have it too.
One thing I would also check is the input jacks and the fx. Loop jacks. There was a period where Nik was the victim of receiving some fake Cliff Jacks that resulted in reduced connectivity within the jack connectors over time.

[psychic fuzz]

It could be any number of things .

For starters.

Does the issue take place right away, or does the amp have to warm up some ? If it uses carbon Comp resistors then one of the plate load resistors might be going south.

If one is going bad then you might as well shot gun it and replace all the plate load resistors in the preamp and PI section.

Have you had the amp open yet ? It might have had some mod's done to it and or parts replaced and there's a poor solder connection now due to that.

Hey there thanks for the input.

I would say it happens after warm up. Also sometimes guitar can be heard on "standby" which is odd. It's faint but you can hear it.

I haven't had the chance to open yet, but it does have carbon comps. I'll attach pics sent by seller. Hopefully this weekend I can crack it open myslef

DZ30-14 (1).jpeg

DZ30-13.jpeg

DZ30-11.jpeg

[psychic fuzz]

My first amp I built was that amp kit and I still have it too.
One thing I would also check is the input jacks and the fx. Loop jacks. There was a period where Nik was the victim of receiving some fake Cliff Jacks that resulted in reduced connectivity within the jack connectors over time.

Interesting, maybe I'll try replacing the jack. Thanks!

[Stevem]

It’s not your input Jack.

This new info that you posted up about hearing the guitar lightly even in the off position and along with the crackling issue points directly to a bad standby switch period!

You should replace it with a double pole single throw switch ( DPST type) that you wire up each side in parallel so you have twice the contact area and in turn twice the switch life.

[award70]

The picture shows a resistor in parallel with the standby switch (like Merlin recommends). That probably explains some signal getting through when in standby.

[Stevem]

Jump out the switch with clip leads and then does the amp still crackle?

[psychic fuzz]

Jump out the switch with clip leads and then does the amp still crackle?

Hey sorry for the delay in response. How do I go about doing that? Never done before thanks!

[psychic fuzz]

It’s not your input Jack.

This new info that you posted up about hearing the guitar lightly even in the off position and along with the crackling issue points directly to a bad standby switch period!

You should replace it with a double pole single throw switch ( DPST type) that you wire up each side in parallel so you have twice the contact area and in turn twice the switch life.

Sorry for the delay in response been crazy busy over here.

So yeah confirmed in STBY i can hear the guitar if I crank the master volume.

AS far as crackling it seems to only happen if I unlpug cable when amp is "ON", to switch channel inputs for instance...

[psychic fuzz]

Another quick update. I played the amp for about an hour. When I went to take the chassis out 2 hours later I noticed the transformers were still warm to touch. Not hot definitely warm. Is that normal?

Here are some pics. Apologies for the bad lighting.

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[Roe]

2 hours later I noticed the transformers were still warm to touch. Not hot definitely warm. Is that normal?

yes normal with the 50r bias resistor and the current draw you get.

bad el84s can easily crackle though

[psychic fuzz]

I know literally nothing about matchless Amps. Still learning. Do you suggest I change that value?

[Roe]

I know literally nothing about matchless Amps. Still learning. Do you suggest I change that value?

NO!

[R.G.]

Another quick update. I played the amp for about an hour. When I went to take the chassis out 2 hours later I noticed the transformers were still warm to touch. Not hot definitely warm. Is that normal?

Yes, as Roe notes.
Dense, heavy things like transformers have a big thermal "capacitance", so they both warm up and cool down slowly. It's the exact analog of an R-C filter. The "R" is the thermal resistance of the heat getting out to the air, and the weight/mass is the capacitance. A transformer as big as both your fists clumped together may have a thermal time constant of one to two hours easily. Five time constants is generally taken as the time for an RC to settle, so a 1 hour time constant trannie can easily take five hours to not be noticeably warm.