18 watt Tremolo TMB POI

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Bieworm
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18 watt Tremolo TMB POI

Post by Bieworm »

For those interested:
I'm in the final process of building an 18 watt Tremolo TMB with a power transformer type PWAM01, supplied by Primarywindings.com
This is a UK based company. This transformer has some really nice features.
1. it's small and kinda lightweight. I'm not sure about the performance yet, but I will be testing in thouroughly in the next few weeks. I ordered 2 of them, and one is already built in an amp that's pretty much ready.
2. the HT secondary is the nicest thing about it. It has a 275-0V winding, tapped at 190V. Theoretically it should do this:
275-0V: 18 watt
190-0V: 9 watt
275-190V: 2 watt

So with this secondary It's like a rudimentary variable B+ system, with 3 fixed B+ supply voltages.

My experiment features a 6A 3-way rotary switch for the B+ switching. This switch has 4x "3 poles + common". I'm using 2 of them for the B+ swichting. I might need the other to switch the bias resistor value, but I'm not there yet.
I'm also not sure if the tremolo will get enough supply voltage for it to start oscillating.. but we'll see if it does in a few days.

This topic may be welcome in other 18W builds. It may be a nice amp to gig AND to play at home with that nice 18 watt overdrive at lower volumes. Although I've built a 1.8 watt plexi with that transformer, which turned out to be pretty loud too...

I have no commercial interest in PrimaryWindings.com, but I'd like to share this with people looking for this kind of thing...
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geoff 1965
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Re: 18 watt Tremolo TMB POI

Post by geoff 1965 »

I had one of those initially in my 18W same as ampmaker used to supply,good transformer with no vibration or heat issues,I only used the 275 & 190 taps and the 190 tap gave earlier breakup with no loss of tone and did’nt try the 2W option so you’ll have to give us a report on that. swapped mine out for a centre tapped 275-0-275 so I could use an EZ81.
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Re: 18 watt Tremolo TMB POI

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geoff 1965 wrote:
Tue 01/25/22 6:49 am
I had one of those initially in my 18W same as ampmaker used to supply,good transformer with no vibration or heat issues,I only used the 275 & 190 taps and the 190 tap gave earlier breakup with no loss of tone and did’nt try the 2W option so you’ll have to give us a report on that. swapped mine out for a centre tapped 275-0-275 so I could use an EZ81.
Will do that for sure! Thanks for the feedback Geoff!
Were you able to use the same bias settings for both B+ voltages?
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Re: 18 watt Tremolo TMB POI

Post by geoff 1965 »

Yeah typical lite2 180R/100uf values on the cathodes Bieworm,both 18 and 9W taps sounded just as good,only difference was earlier breakup.that’s the lite2 circuit though without tremolo.
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Re: 18 watt Tremolo TMB POI

Post by zaphod_phil »

geoff 1965 wrote:
Tue 01/25/22 10:03 am
Yeah typical lite2 180R/100uf values on the cathodes
a 1000uF or 2200uF cap is preferable here, especially when running colder-biased, with a 180R cathode resistor.
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Re: 18 watt Tremolo TMB POI

Post by geoff 1965 »

Noted the cap values on the newer circuits ZP,I was referring more to the voltage drop between 9W & 18W on the biasing,there was no audible difference with the tone of the amp. I think Bieworms concern will be the tremolo circuit especially if he drops to 2W voltages,don’t you have to have certain voltage parameters for the tremolo?
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Re: 18 watt Tremolo TMB POI

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geoff 1965 wrote:
Tue 01/25/22 5:40 pm
Noted the cap values on the newer circuits ZP,I was referring more to the voltage drop between 9W & 18W on the biasing,there was no audible difference with the tone of the amp. I think Bieworms concern will be the tremolo circuit especially if he drops to 2W voltages,don’t you have to have certain voltage parameters for the tremolo?
Maybe tonight we'll know the answer to that😉😉😉... been wondering about it for a loooooong time
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Re: 18 watt Tremolo TMB POI

Post by Daviedawg »

geoff 1965 wrote:
Tue 01/25/22 6:49 am
I had one of those initially in my 18W same as ampmaker used to supply,good transformer with no vibration or heat issues,I only used the 275 & 190 taps and the 190 tap gave earlier breakup with no loss of tone and did’nt try the 2W option so you’ll have to give us a report on that.
My 18 watt has used that same Ampmaker PT since I built it more than 11 years ago. It has an average of at least 5 hours a week on it since then. So pretty reliable. I also only tried the 190 tap before I fitted VVR.

Dd
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Re: 18 watt Tremolo TMB POI

Post by Bieworm »

Daviedawg wrote:
Wed 01/26/22 3:44 am
geoff 1965 wrote:
Tue 01/25/22 6:49 am
I had one of those initially in my 18W same as ampmaker used to supply,good transformer with no vibration or heat issues,I only used the 275 & 190 taps and the 190 tap gave earlier breakup with no loss of tone and did’nt try the 2W option so you’ll have to give us a report on that.

My 18 watt has used that same Ampmaker PT since I built it more than 11 years ago. It has an average of at least 5 hours a week on it since then. So pretty reliable. I also only tried the 190 tap before I fitted VVR.

Dd
Thanks Dd! If you guys say it's ok, it will be ok. That's a relief thus far..
Another relief is that I tested the B+ switching yesterday and I got unloaded:
292V-204V-91V. So far so good!
I have yet to install the cap can, PI plate wiring and output tube wiring and I can start checking for start up. (Wired in the PTx yesterday, and a temporary quick connector for the primary voltage.. see if 230V or 240V gives the best voltages)
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Re: 18 watt Tremolo TMB POI

Post by Bieworm »

Crap! Not gonna know it tonight! There's some serious oscillation going on. Looking for that first...
To be continued

2 things:
It's definitely tremolo related. When I disconnect the grid from the tremolo it's gone.
I put a .1uf cap on the mid by mistake..
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Re: 18 watt Tremolo TMB POI

Post by JMPGuitars »

It looks like you didn't shield your V1 plate wires...
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Re: 18 watt Tremolo TMB POI

Post by Bieworm »

JMPGuitars wrote:
Wed 01/26/22 8:16 pm
It looks like you didn't shield your V1 plate wires...
Shoot!!! Might have to change that..
Probably found the culprit.. it immediately sounded like a grounding issue. Guess what? Forgot to ground my speed pot!!!!! Go figure!!! Lol 😀😀😀

By the way.. I made a stupid error with the switching for tremolo activation. I added a speed pot with on off switch on the dial. When switched it will ground the tremolo grid, but then it will stop wiggling!!! it should be the other way around, so that's impossible with an on off switch with 2 poles. I will be adding a jack input with a parallel toggle switch to activate the tremolo.

Ok, besides fixing that... Isn't it good practice to add a resistor parallel with the gain pot, so in case the wiper fails there's still a grid leak? 10x pot value is ok to leave the pot value uncompromised?
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Re: 18 watt Tremolo TMB POI

Post by Bieworm »

Ok the amp is up and running, voltages set too.. sounds fantastic!!!
18W super
9W super
2W.. well, pretty ok for quiet stuff at home.

But: here comes!!! No trem on the 2W setting.. as expected. 18 and 9 trem's superb tho...
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Re: 18 watt Tremolo TMB POI

Post by geoff 1965 »

Yes that was expected really with the 2W voltages,Dd mentioned he lost tremolo on the low voltage side of his VVR.
How is the earlier breakup on the 9W setting?
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Re: 18 watt Tremolo TMB POI

Post by Bieworm »

geoff 1965 wrote:
Thu 01/27/22 3:40 pm
Yes that was expected really with the 2W voltages,Dd mentioned he lost tremolo on the low voltage side of his VVR.
How is the earlier breakup on the 9W setting?
Nice and thick! Pretty obvious volume drop, but still giggable
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