*Resolved* MOD The Wave Reverb Tank Kit PT DOA? *Yes DOA*

[alvodicka]

Hi,
First off I'm new to the forum and definite noob to the art/craft of amp building.

I've build a couple dozen pedals. Used to be a residential/commercial electrician by trade. Like working with diy electronics etc. I started building pedal kits over the shutdown. Loved it. And part of me couldn't stop exploring diy rig gear.

I started to get the itch to try an amp kit. But before I took on an amp kit build. I thought I better start with the MOD tube reverb kit.

I completed putting the reverb kit together and checked and double checked components etc. Plugged her in and the unit worked great for about 10 minutes. Then the volume started to drop and the PT started smoking. The lamp went out and I'm sure the pt is fried.

I immediately ordered a replacement PT.
And then started wondering do you ever get an DOA Power transformer? My noobness knows its probably an error in my build that shorted it out or something. But the fact that it worked fine for 10 min I would guess probability would be 98%user error 2% bad transformer.

Any thoughts, ideas, comments, suggestions would be greatly appreciated. Thank you!

[martin manning]

The PT is toast. It might have been defective, and you should be able to determine that. Here's the power supply. I would start by disconnecting all secondary leads from the PT, and then measure resistance to ground from the places where you disconnected the leads. You should get infinite resistance from either side of the heater string to ground, and a few tens of k-ohms from the inputs to the diode bridge to ground. I don't like the cap bleeder switch with the 1Ω 5W. It's an ok idea, but I would make that resistor at least 1kΩ 5W. As it is, it all but shorts the 22uF it is connected to, and that will damage the capacitor.

[Stevem]

What I find odd is that if the kit was fitted with the right 1 amp fuse that the kit calls for then with a bad PT the fuse should have blown.

Who knows, maybe the fuse was right on the edge of blowing when you turned it off.

Before you fire it back up I would build a light bulb limiter to run it on, or set it up with .750 amp fuse at first.

[Phil_S]

That second switch with the 1Ω resistor looks very strange to me. What is its purpose? Is it needed? I think, if I was building that circuit, I'd be more than tempted to omit it.

[xtian]

That second switch with the 1Ω resistor looks very strange to me. What is its purpose? Is it needed? I think, if I was building that circuit, I'd be more than tempted to omit it.

When you turn the power switch off, the second pole of the power switch is meant to connect the 1R resistor to dump B+ to ground. I agree, that's nuts (arcing on the switch, at the least, plus stress on the caps), and as Martin suggests, 1K is a far better choice.

If OP was to accidentally wire the power switch incorrectly, with the 1R resistor connected to ground at the same time power is applied to the circuit, that would burn out the PT quickly.

[alvodicka]

Ok thanks for the replies!

I will check these things out this afternoon and report back. I appreciate the input. Thanks.

[alvodicka]

Ok so the power switch is correctly wired. And I swapped the 1ohm 5w for a 1k5w. Just to get that out of the way.

Built an LBL for when I get to that point.

Looking at V2 I have the 9/4,5 swapped from v3. I had read before I fired her up the other day that it didn't matter. So to be proper I swapped them to be all 9's and all 4,5's.
This would not be a potential culprit? Just a potential noise inducer right?

Resistance to ground
Heater wires are both infinite resistance to ground.

Inputs to diode bridge resistance to ground are 63.7k and 64.3k.

Is this looking like a bad PT?

Thanks for the input and help. I appreciate it.

[martin manning]

That all sound good, and yes it appears that the PT was defective. I would try connecting a new one with your limiter and see if it works.

[alvodicka]

Thanks
I'll swap the new one in this evening or over the weekend and report back. Thank you!

[alvodicka]

So I briefly ran the unit through the light bulb limiter with a 40 watt bulb. The bulb did in fact dim. Meaning there is no short.

Fired her up and it works great!

Thanks for your help I appreciate it!

[martin manning]

Nice! Now maybe you can get a refund for the dead one. I’d say this unit is as complex as a lot of amps, so onward and upward!

[alvodicka]

Thanks I sent an email this afternoon re:refund.

I am itching to start an amp project.

I've built way more complex pedals compared to "the wave" for sure. But wanted an intermediary tube/transformer project first.

there's the build and then there's the understanding the build.

So gratifying and enjoyable to build and learn and then fun to play.

I've been enjoying browsing the forum.

Thanks!