Hilbish/Matamp GT120 Transformer question.

[MadAsAHatter]

I’m not sure if I'm reading/comparing these transformer specs correctly or it the I got will not work on the Hilbish Matamp GT120 clone.

I asked Hilbish which transformer for recommendations and his response was “the Mercury one is fine”. @ClintN667 recommended one from Heyboer since he was working on a similar build. I went with the Heyboer set. Comparing the PT spec sheet between the Mercury & Heyboer I noticed the voltages were different.

Given these specs sheets below, Are they just written differently, I'm reading/comparing them wrong, and both transformers are comparable? Or is the Heyboer one a no-go and I need to get the Mercury? I suspect it's the former, but I want to double check.

A secondary question to this:
Both transformers show to have a secondary low voltage tap; 6.3v on the Mercury & 15v on the Heyboer. In the diagram below it shows using the second 6.3v tap on the Mercury to supply voltage to the preamp heaters (orange & yellow twisted wires). Could I use the 15v tap on the Heyboer for the same purpose? Or is this tap for something else like powering a relay board? If the latter is the case, then would I just use the main 6.3v tap on the Heyboer for both pre & power tube heaters?

 

[ClintN667]

Hey man. Sorry for the late reply. Do you have facebook? I recommend joining this group https://www.facebook.com/groups/moderntubeampevolvediy/ it's ran by Alex Catlow who spec'd that PT and he basically used the hillbish schematic and designed his own board. There is also a mistake that he found on the NFB circuit that he can chime in on. Him and Jason Tong, Bruce Egnater, Dave Friedman and a few others frequent that group regularly. We just had a tornado come through my yard on Wednesday so I'm trying to get everything back up to pre storm(power just got back on about 2 hours ago.) Post this there and Im sure the group will get you sorted.

 

[MadAsAHatter]

Sorry to hear about the tornado. I'm assuming since your posting here your family was all safe. Hopefully you don't have any major damage to deal with.

I remember you saying that Alex spec'd his design based on the Hilbish schematic; which is supposedly a recreation of the vintage Matamp design. That's why I was surprised to see the secondary voltage difference. I expected some difference, but not 360V vs. 186V. But I also know that manufacturers don't necessarily write out the specs in the same way and I'm likely reading them incorrectly.

I don't do facebook much, but I've been a part of that group for a bit. I just looked and someone just asked a similar question about transformers for the Hilbish. Even though they're asking about a Hammond PT, from the specs posted that had some extra info included I think I extrapolated what I needed to answer my question.

I'm fairly certain I was reading the Heyboer specs wrong. It looks like the Heyboer posted spec to show Red to Grey as 360V so Red to Red(common) and Grey to Red(common) should be roughly half that at 180V each. That make more sense and lines up better with the Mercury specs.

I believe my speculation on the 6.3V tap was correct. I'll have to use that for all the tubes which hopefully should have enough current to power everything. Though I'm not sure if I can put in a terminal strip to "split" it to the power tubes and preamp tubes. Or if I need to run it all in series to the power then preamp tubes (or vice-versa). I think I'll use the 15V tap to power an indicator light that can run on that voltage.

 

[ClintN667]

Sorry to hear about the tornado. I'm assuming since your posting here your family was all safe. Hopefully you don't have any major damage to deal with.

I remember you saying that Alex spec'd his design based on the Hilbish schematic; which is supposedly a recreation of the vintage Matamp design. That's why I was surprised to see the secondary voltage difference. I expected some difference, but not 360V vs. 186V. But I also know that manufacturers don't necessarily write out the specs in the same way and I'm likely reading them incorrectly.

I don't do facebook much, but I've been a part of that group for a bit. I just looked and someone just asked a similar question about transformers for the Hilbish. Even though they're asking about a Hammond PT, from the specs posted that had some extra info included I think I extrapolated what I needed to answer my question.

I'm fairly certain I was reading the Heyboer specs wrong. It looks like the Heyboer posted spec to show Red to Grey as 360V so Red to Red(common) and Grey to Red(common) should be roughly half that at 180V each. That make more sense and lines up better with the Mercury specs.

I believe my speculation on the 6.3V tap was correct. I'll have to use that for all the tubes which hopefully should have enough current to power everything. Though I'm not sure if I can put in a terminal strip to "split" it to the power tubes and preamp tubes. Or if I need to run it all in series to the power then preamp tubes (or vice-versa). I think I'll use the 15V tap to power an indicator light that can run on that voltage.

Yeah we were safe thankfully. Was without power for a few days. I just sent Alex this link so hopefully he can respond. I'm still relatively new to building so I don't feel comfortable with my answer. I would hate to tell you wrong and get shocked.

 

[MadAsAHatter]

Yeah we were safe thankfully. Was without power for a few days. I just sent Alex this link so hopefully he can respond. I'm still relatively new to building so I don't feel comfortable with my answer. I would hate to tell you wrong and get shocked.

Glad to hear everyone was safe and power loss and some cleanup was the worst of it for you.

I asked about the heater wires in Facebook group and got my answer there. I'll be able to run everything off the 6.3V leads and can either run it all straight in a line or split it off a tag strip to pre and power tube sockets.

I DM'd Alex about the PT specs as well. One way or the other I'll get it all figured out.

 

[ClintN667]

Glad to hear everyone was safe and power loss and some cleanup was the worst of it for you.

I asked about the heater wires in Facebook group and got my answer there. I'll be able to run everything off the 6.3V leads and can either run it all straight in a line or split it off a tag strip to pre and power tube sockets.

I DM'd Alex about the PT specs as well. One way or the other I'll get it all figured out.

Good deal. I spoke to Alex the other day about this and meant to follow up here. Alex and that group is a great resource.

 

[MadAsAHatter]

Good deal. I spoke to Alex the other day about this and meant to follow up here. Alex and that group is a great resource.

Between Alex and another good amp tech I know I was able to get everything figured out. I'd be able to use the transformers with a few minor modifications; eliminate one connection and possibly change 2 resistor values. The voltages would change a bit but still be acceptable values. Even though it seems pretty straight forward I feel I'm still too much of a novice to change something that's not fully laid out. My comfort level is still at following the exact layout.

What I'm thinking I'm going to do is put the Heyboer transformers aside for now and get the Mercury ones for the Hilbish. After I finish with this project I'll get a board from Alex and build his version with the Heyboers. From what Alex posted his is a MV version where the Hilbish is NMV so they should be different enough from each other. Plus it'll be another fun project.

Since you bought Alex's board what documents came with it? Are they easy enough for a novice to follow?

 

[ClintN667]

Between Alex and another good amp tech I know I was able to get everything figured out. I'd be able to use the transformers with a few minor modifications; eliminate one connection and possibly change 2 resistor values. The voltages would change a bit but still be acceptable values. Even though it seems pretty straight forward I feel I'm still too much of a novice to change something that's not fully laid out. My comfort level is still at following the exact layout.

What I'm thinking I'm going to do is put the Heyboer transformers aside for now and get the Mercury ones for the Hilbish. After I finish with this project I'll get a board from Alex and build his version with the Heyboers. From what Alex posted his is a MV version where the Hilbish is NMV so they should be different enough from each other. Plus it'll be another fun project.

Since you bought Alex's board what documents came with it? Are they easy enough for a novice to follow?

He has boards for the Mata Amp clone, ST1 boards that are pretty much dead on and he also has SLO boards. His iron will work on all of them. He has schematics and a really good layout for the Mata and Slo. I have populated the slo PCB but I'm laying off of building for awhile until I get some more space to work.

Let me see if I have the layout and I will send it to you.

 

[RedPlated]

The Heyboer appears to be a 50w transformer and the Mercury is 100w. Full wave vs half wave rectifiers. 50w AC secondaries are higher due to rectification style. That’s why the voltages are different.

Notice there is also no bias supply on the Heyboer. A 50w PT uses one side of the high voltage secondary for the bias supply.

The yellow 15vac supply is to be rectified to DC and used for heaters, relays, etc…