Hilbish/Matamp GT120 Transformer question.

MadAsAHatter

Well-known member
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?


1714579312106.png

1714579377087.png


1714582869632.png
 
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.
 
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.
 
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.
 
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.
 
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.
 
Back
Top