Rob Robinette's Micro Champ EF80 Power transformer EU equivalent question.

RicciAntoni_07

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Red red secondary are just like your white/yellow on the Antek and go to the bridge rectifier . Green/green go to the lamp/heaters. I think your Primaries should be black/violet .

Check with others before wire as above.
Thanks, I will.
 

2L man

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It is good practice to measure voltages when build advances and then you know what point possible problem was done. I measure PTs and OTs first before installing them because it takes only few minutes. When they are made obviously it is still hand labor on critical steps when input/output wires or solder lugs are installed and sometimes mistakes are made.

Only problem there is that sometimes electrolyt voltage rating is selected assuming tubes conduct and cause voltage grop to circuit but then they are selected wrong.
 

2L man

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This picture has typical OT measuring but I measure PTs same way: I input Mains which here is quite accurate 230VAC but I measure it exactly and that to the CT wire/tab there comes 115V when OT is a push pull. Before inputting Mains I have measured all winding resistances so I know I input mains to the full Primary coil. Then I measure all outputs and I calculate winding ratios and know that OT function and what the outputs truly are.
PHOTO-2022-04-18-15-49-07.jpg
 

RicciAntoni_07

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This picture has typical OT measuring but I measure PTs same way: I input Mains which here is quite accurate 230VAC but I measure it exactly and that to the CT wire/tab there comes 115V when OT is a push pull. Before inputting Mains I have measured all winding resistances so I know I input mains to the full Primary coil. Then I measure all outputs and I calculate winding ratios and know that OT function and what the outputs truly are. View attachment 974897
Wow!!! So helpful! Critical. thank you! I will be doing this very very soon. I think because I got the wrong size chassis I will wait until later this week when it arrives. Since I am a beginner I think this smarter to have a bigger chassis, at least way more space than the one I originally bought. I really appreciate the precision of this photo--that helps a ton with explaining. We need more clear photos explaining stuff, I rarely see pics on forums.
 

RicciAntoni_07

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Hello, I wanted to ask you, and anyone else a few questions as I begin to embark on this first amp build odyssey. I got the PT here and I wanted to see if I am correct about these numbers
--All in one heat sync wrap--

BK wire has 0v.
Yellow wire has 120v.
Violet 230v.
Red 240v.

other side of the PT

Secondary 1--RED RED 200V
Secondary 2--GREEN GREEN 6.3v


I am going to try to learn as much about all this as I can before I start, but just wanted to see what feedback I'd get here first! As far as the layout goes, I'm not there quite yet. Because I have a different PT, I am not 100% sure what goes where. I don't have the power chord with the Black, White, and Green wires--not entirely sure what to get for that. They layout for the EF80 version has different wires and wiring. If you could clarify that'd, it would help me a lot!

Appreciate the feedback!
Can anyone tell me what this power chord is with the Black, White, and Green wires?
 

RicciAntoni_07

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Green is earth ground, white neutral, and black hot.
yes, I know that :) I didn't pose the question well I think. I bought everything except whatever has these three wires. I don't see where the come from. My power chord doesn't have open wires. I'm just confused where those three wires come from.
 

Paul-T

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You're in the EU, right? In which case your hot is brown, neutral blue and ground/earth is green/yellow. Again without looking at your chassis you would either have a captive mains lead or use an IEC connector. IF the former, a lot of high street hardware stores will sell.
 

RicciAntoni_07

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You're in the EU, right? In which case your hot is brown, neutral blue and ground/earth is green/yellow. Again without looking at your chassis you would either have a captive mains lead or use an IEC connector. IF the former, a lot of high street hardware stores will sell.
Are you using an IEC connection or are you going to hook straight from the all plug to the inside of the amp. Cut the non wall plug end of the power cord and strip the housing back.
Wangdaning, I was thinking that is what I need to do--to cut and strip the housing back. Thanks!!

I will have captive mains lead I think. I am still organizing all this. I've been working on pedals these last few weeks, while I waited for parts to arrive for the amp. I"m in the EU yes.

I will look into the IEC connector too. Not entirely sure yet between the two. Do you recommend one over the other?
 

wangdaning

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I used the former and it works fine. If your chassis does not have a cutout for an IEC connector I would go with this method (unless you can easily make the hole yourself).

This is what I did, and my wires are Euro colors (guess China uses those as well).
Power Wiring.jpg
 

RicciAntoni_07

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Nice. I will need to look into all this a bit more. I am able to make holes, but not squares. My chassis I will have to make all the holes myself. I'll come back here in a few days and ask the questions I will probably have. Thanks!
 

2L man

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I use always IEC-connector when it is possible to install because of versality. Then it is allowed to use smaller and cheaper single pole Mains Switch too. Yes it is more work to make hole for it but to aluminium chassis quite easy and take about 20 minutes. I just draw outline and drill 3mm holes about 4mm apart and use strong wire cutters to cut it open and then file the hole clean.

There is an IEC punch but they are very expensive. Also a "nibber" which easily cut "crescents" from aluminium starting from pilot hole but all I know are expensive. Plate cutter which work like scissors are cheaper but they do not work for IEC socket holes
 

RicciAntoni_07

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I use always IEC-connector when it is possible to install because of versality. Then it is allowed to use smaller and cheaper single pole Mains Switch too. Yes it is more work to make hole for it but to aluminium chassis quite easy and take about 20 minutes. I just draw outline and drill 3mm holes about 4mm apart and use strong wire cutters to cut it open and then file the hole clean.

There is an IEC punch but they are very expensive. Also a "nibber" which easily cut "crescents" from aluminium starting from pilot hole but all I know are expensive. Plate cutter which work like scissors are cheaper but they do not work for IEC socket holes
Good idea about making the square! I am not even sure where I can source the connector. This build is probably not meant for first time people. There is some information that is left out, or assumed the person knows. I got everything on the BOM, but no idea about this IEC and I didn't know I needed to strip the power chord to have those wires. I've lost a bit of momentum because of these question I have to find answers to.
 

Len058

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https://www.tube-town.net/ttstore/power-jack.html

But you can get them at many places. It is standard for desktop pc's, many guitar amps, some laptop chargers, etc.

It might be wise to measure the voltages on a sunny day. If you live near a lot of solar panels, the voltage can go up quite a bit. The mains voltage may vary, max 10%. As someone mentioned above it's probably better to choose the 240 wires of the PT.

I live in Les Pay-Bas and the voltage was 236 when I measured it.
 
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RicciAntoni_07

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https://www.tube-town.net/ttstore/power-jack.html

But you can get them at many places. It is standard for desktop pc's, many guitar amps, some laptop chargers, etc.

It might be wise to measure the voltages on a sunny day. If you live near a lot of solar panels, the voltage can go up quite a bit. The mains voltage may vary, max 10%. As someone mentioned above it's probably better to choose the 240 wires of the PT.

I live in Les Pay-Bas and the voltage was 236 when I measured it.
:) nice, love the pay-bas! Thanks, I will for sure use the 240 wires. For IEC connector I have this as the power chord. This is the thing I am missing-but what I don't understand is how I get the power chord wires--the hot, neutral and ground. I still don't see where that comes from.
 

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Paul-T

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I've done both. If you haven't had that much experience (and dont' have drill, good jig saw etc) captive is absolutely fine. Just take an existing one and cut off the end.
 

Len058

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This is the thing I am missing-but what I don't understand is how I get the power chord wires--the hot, neutral and ground. I still don't see where that comes from.
The one in the middle is ground. I don't know which one should be hot or neutral but you can measure it. Just plug the cable in and check with a voltage tester.

Over here we don't have polarised plugs so it doesn't matter how you connect hot and neutral. You could ignore the hot and neutral and it will work. As long as you make sure the safety ground is connected, you won't be harmed.

I just checked my amp and I used a 16 ohm dropping resistor after the diodes to get the EF80 plate voltage to 294 Volts.
 

wangdaning

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Yeah, your choice is to cut the end off and do it captive by tripping back the main black housing and exposing the inner wires. With the IEC you will have to solder to the pins on the back of the IEC housing and then make sure they connect to the appropriate places. You should be able to find a generic guide on IEC wiring easily, then just think of what you solder as the equivalent from the instructions you have. Something like this.
B1063775020.jpg
 




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