Power Transformer for 100 watt 183

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donvan
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Power Transformer for 100 watt 183

Post by donvan »

I'm close to starting my first build. After listening to a lot of tone clips I decided on going with a 100 watt #183 clone but I like to get my ducks in a row before jumping in.

I see an issue with the 183 schematic that is posted in the dumble files. It calls for a MOJO763 or TF130 power transformer. If my understanding is correct, these transformers are spec'ed for a 6 amp heater winding. I don't think this is near enough for a #183 which has 4 EL34s. The EL34s alone need 6 amps of heater current. The other 3 AX7s need another .9 amps total and the lamp needs a little something too right? That gets us up to around 7 amps. I think a little head room doesn't hurt either.

In my opinion, the power transformer for a #183 would need somewhere around 7.5 amps for the heaters.

What is everyone around here using? I have a hard time believing that everyone who builds a 100 watt #183 is having a custom power supply transformer built. Can someone help me out with this?

Thanks!
Don
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pompeiisneaks
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Re: Power Transformer for 100 watt 183

Post by pompeiisneaks »

You're definitely right that the EL34's pull 6A for 4 tubes, 1.5 per, so I'm guessing you're right in that way, but there's got to be some common PT's used for 4xEL34's like for marshall 100 watt amps no? I'm curious what others have used too, but I'd bet something like this should work fine: https://www.tubesandmore.com/products/t ... ower-100-w. I'm not sure where you're thinking you need 7.5A though, a 12AX7 uses 100mA of current for heaters, so you need 300mA total for that and if you wanted say to add the Dumbleator inside it, that's only another 100mA so you're at 6.5mA max needed for heaters. Or maybe I'm doing the math wrong there heh.

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xtian
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Re: Power Transformer for 100 watt 183

Post by xtian »

Don, here is my thread on the #183 I built in May 2017.

I used ClassicTone iron, and am very pleased with the results. PT is 40-18004, and OT is 40-18102. And I got my choke from tubesandmore.com.

Sure, you're right about the heater current! But in practice, it seems fine--PT does not get hot.
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norburybrook
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Re: Power Transformer for 100 watt 183

Post by norburybrook »

can I ask a couple of relevant questions too about this?

Could I use the peavey 120w Deuce iron I have for a #183 EL34 build?

It would probably be putting out 500v rectified , is that OK for a set of JJ?'s or whatever new valves anyone recommends,? I know JJ6L6's are fine at that voltage.

I suppose if things started getting out of hand I could always swap to a set of 6L6's.


and:

I have a spare 20-0-20 secondary tap,could I use just the 20-0 into the rectifier board and then use a 12v regulator and 12v relays, instead of my normal 5v ones?

TIA

Marcus
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martin manning
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Re: Power Transformer for 100 watt 183

Post by martin manning »

Which Deuce? 4x 6L6? That doesn't look promising to me. Maybe start a new thread.
donvan
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Re: Power Transformer for 100 watt 183

Post by donvan »

pompeiisneaks wrote: Wed Jul 26, 2017 10:29 pm You're definitely right that the EL34's pull 6A for 4 tubes, 1.5 per, so I'm guessing you're right in that way, but there's got to be some common PT's used for 4xEL34's like for marshall 100 watt amps no? I'm curious what others have used too, but I'd bet something like this should work fine: https://www.tubesandmore.com/products/t ... ower-100-w. I'm not sure where you're thinking you need 7.5A though, a 12AX7 uses 100mA of current for heaters, so you need 300mA total for that and if you wanted say to add the Dumbleator inside it, that's only another 100mA so you're at 6.5mA max needed for heaters. Or maybe I'm doing the math wrong there heh.

~Phil
Thanks Phil. This Marshall transformer might be an option. The 7 amp heater current rating looks good. But is the 290 ma secondary beefy enough? 290 ma seems a little low.

Back on the heater current - you mentioned that the 12AX7 just need 100 ma of current for the heaters. My understanding is that they need 300ma if connected in parallel and 150ma if connected in series. Aren't they connected in parallel?
donvan
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Re: Power Transformer for 100 watt 183

Post by donvan »

xtian wrote: Wed Jul 26, 2017 10:31 pm Don, here is my thread on the #183 I built in May 2017.

I used ClassicTone iron, and am very pleased with the results. PT is 40-18004, and OT is 40-18102. And I got my choke from tubesandmore.com.

Sure, you're right about the heater current! But in practice, it seems fine--PT does not get hot.
xtian, thanks for the response. I'm glad the ClassicTone iron is working well for you. The spec shows that it only has 5.5 amps of heater current capacity - .5 amps less that the mojotone. With the EL34's alone requiring 6 amps that really scares me. I need to find another option.
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Re: Power Transformer for 100 watt 183

Post by pompeiisneaks »

donvan wrote: Thu Jul 27, 2017 6:16 pm
pompeiisneaks wrote: Wed Jul 26, 2017 10:29 pm You're definitely right that the EL34's pull 6A for 4 tubes, 1.5 per, so I'm guessing you're right in that way, but there's got to be some common PT's used for 4xEL34's like for marshall 100 watt amps no? I'm curious what others have used too, but I'd bet something like this should work fine: https://www.tubesandmore.com/products/t ... ower-100-w. I'm not sure where you're thinking you need 7.5A though, a 12AX7 uses 100mA of current for heaters, so you need 300mA total for that and if you wanted say to add the Dumbleator inside it, that's only another 100mA so you're at 6.5mA max needed for heaters. Or maybe I'm doing the math wrong there heh.

~Phil
Thanks Phil. This Marshall transformer might be an option. The 7 amp heater current rating looks good. But is the 290 ma secondary beefy enough? 290 ma seems a little low.

Back on the heater current - you mentioned that the 12AX7 just need 100 ma of current for the heaters. My understanding is that they need 300ma if connected in parallel and 150ma if connected in series. Aren't they connected in parallel?
Oh actually you're right, I don't know waht I was thinking, but you're talking the 183 which has only 3 tubes so 900mA you're still at 6.9A and under 7. Also I think others have stated, they quite often give you breathing room on those windings.

as for the question on the mA needed on the main secondary winding, the 12AX7's push 1.2 mA or so, so next to nothing, the EL34's per pair push maybe 60mA, so 120 total (depending on how hot they're biased of course), I'm pretty sure your 290mA should be fine.

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pompeiisneaks
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Re: Power Transformer for 100 watt 183

Post by pompeiisneaks »

Even more detail on PP operation, at 430V the datasheet I'm looking at says that max anode current should be 70mA and g2 14mA so you shouldn't be seeing more than 100 per pair.

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donvan
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Re: Power Transformer for 100 watt 183

Post by donvan »

Phil, thanks for the responses! One other thing. The Marshall has slightly higher secondary voltages - 350v instead of 340v. Would I need to make any adjustment for that or do you think it's close enough?
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Re: Power Transformer for 100 watt 183

Post by norburybrook »

That won't make any difference I've found. You just bias accordingly for your power valves and the pre amp valves can be adjusted with the dropping string if needed. However I've found that 10- 20 volts here are the make no audible difference to me.

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drew
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Re: Power Transformer for 100 watt 183

Post by drew »

If you're in the US, why not just have Heyboer make one to your specs?
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dreric
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Re: Power Transformer for 100 watt 183

Post by dreric »

When I built my 183, J Boarders have Heyboer make up some over spec'ed tiwn transformers. There were called "Black Face Twin Plus" HTS-10359 9961409. They have the heater current you want plus a tap for the relays! With the part # they will make one for around $120

Good luck!
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martin manning
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Re: Power Transformer for 100 watt 183

Post by martin manning »

Wow, awesome! Thanks for the tip ;^)
donvan
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Re: Power Transformer for 100 watt 183

Post by donvan »

dreric wrote: Sat Jul 29, 2017 3:02 pm When I built my 183, J Boarders have Heyboer make up some over spec'ed tiwn transformers. There were called "Black Face Twin Plus" HTS-10359 9961409. They have the heater current you want plus a tap for the relays! With the part # they will make one for around $120

Good luck!
That is exactly what I'm looking for. Thanks!
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