Heyboer PWR TRANSFORMERS for MOJO 5E8A TTLP AMPS

[avguy49]

I am looking to find a few others who are interested in going in with me to have a small lot of special wound Heyboer Pwr Trannys made up for the Mojo TTLP 5E8A kit. The MOJO752 tranny that comes with the kit has a 5V winding rated at 3Amps and 2 5U4GB rectifiers pull 6A on the 5V winding. I have been in contact with Phil at Heyboer and has has a replacement transformer that is upgraded on both the 5V and 6.3V windings to 6A and 7.5A respectively. These have to be bobbin wound due to the increased wire size, etc. so this is not a production model transformer. If we can get a few guys together that want this transformer we can get a little bit knocked off the price. Just drop me a note on this post and let's see if we can get a few of us together.
~Thanks,
~Avguy49

[Bob Arbogast]

Do you have a price for the PT?

Thanks.

Bob Arbogast

[avguy49]

I am checking on that Bob. Will post it when I get a reply from Phil at Heyboer. I was just curious if there was anyone else interested in one right off the bat. I just sent another email to find out a price for one vs say 5 or 10 of them.
~Philly

[avguy49]

Ok, here's the scoop, I got a reply from Phil with Heyboer with the pricing and part number for this tranny. Part number is: HTS-7281-2B single tranny price is $150.00, at 10 units the price drops to $120.00 each. This gives a full 5V 6A and 6.3V 7.5A windings and should run a lot cooler with no strain at all on it. This should give the TTLP some bark!
Thanks,
~avguy49
~Philly

[Wally]

Phil, why not just build the amp with a GZ34 rectifier tube, which would be simular to the 2 X 5U4 situation regarding sag and such. There would be less expense regarding sockets, tubes, wiring time, etc. If someone wants the 'sag' of a single 5U4, that kit PT will handle one of them with no problem, right? Just a thought.

[Wally]

Phil, Ill try not to bother your design too much; but this just occurred to me.
Wouldn't it be possible to use those two rectiifer sockets in a different manner.....make one a 5U4 and one a GZ34? Make them swtichable for the 'harder' GZ34 votages and the option for the single 5U4 voltages???
Imho, this would make the amp more quickly versatile than the original design while maintaining the original intent...hgiher voltage and more punch, right?

[Wally]

Editted

[Wally]

editted

apologies if I stopped any conversation here. So,....bump!

[avguy49]

No problem Wally, just been busy dude.

[muchxs]

The 5E8A runs 4x 5881 tubes. That's asking a lot of a single 5AR4. A 5AR4 is a perfect match for 2x EL34s. It's practically designed for that application.

The 5E8A was a monster for its day. Four power amp tubes! Two rectifiers!

The original Triad PT is a little wimpy. After all, who would crank an amp like a tweed Twin in 1959?

There is an organ amp that uses a Triad PT one part number away from a '50s Fender / Triad. It has a 4a / 5v rectifier winding. I like to buy them cheap (less than a new Heyboer) so that's all I'll say in a public forum.

[avguy49]

The 5E8A has 2 x 5881/6L6 and 2 x 5U4 rectifiers and comes in at about 40W. It is the 5F8A that has 4 x 5881/6L6 and one 5AR4/GZ34 rectifier and runs about 80W.

The original thing I was talking about is this Heyboer Trans that was built up some time ago for another guy on this forum for this same kit/amp the Mojo LPTT or 5E8A circuit. Heyboer now has an actual part number for it but it is a one off build to order transformer. I am probably going to replace the original Mojo power trans with the Heyboer when I get the time in a few months. The original guy that ordered it said that it was much more responsive and ran cooler but was heavier which is not that big a deal to me. Don't get me wrong, the amp is smokin' and sounds great and runs quiet as a mouse since I star grounded it and heavily modified the grounding configuration but I am looking for a little more out of it.

[dvlsadvc8t]

I've actually been a member here for a while but never had anything to contribute so this is my first post. Anyway, Avguy, I have a Marsh LPTT which is pretty much the Mojo kit. I also have that Mojo 752 tranny. In fact, mine is the 752EX tranny. Ever since I got this thing together, I have felt like it had zero power to it. At first, I thought it was my imagination since it does sit next to my Twin Reverb. But after talking to a buddy today and telling him that I was just standing 3 feet in front of the amp with the volume on 9, I am convinced that there's an issue. He says his experience with LPTTs is that it'll blow you out of the room on 4. Are you having the same issue? I notice that the spec sheet for the Mojo tranny I got says that it's for a Bassman. Even the Mojo site shows that they use a Bassman tranny for the LPTT. That can't be correct. I have to think that this is why I am experiencing such low volume. Mercury Magnetics has 2 different trannies for the 2 amps. Is this what Mojo is trying to correct with what you are talking about? Basically, have you been experiencing the same thing I am? Thanks.

[avguy49]

Hey buddy, I am with you 100% and plus some. I not only believe there is an issue with the PT specs, but the OT originally was the problem I had with Mojo. I am a Mojo dealer and I like their stuff a lot but the PT and OT on this deal just plain SUCK. I emailed back and forth with them about the transformer docs telling them that the output I was getting out of the amp just wasn't right. I was only pulling minimal wattage out of it. Finally I did the old reverse calculation trick from the secondary to check the primary impedances and discovered that their docs on the OT had the color codes wrong. Still, after fixing them I am only getting maybe 25 watts out of it and that is downhill with the wind to my back on a good day. I think that the PT AND the OT are BOTH wrong. I think the PT doesn't have enough current capacity behind it to support both the 5U4s correctly AND I think the size and primary impedance of the OT is way wrong. When I worked my secondary to primary turns ratio to calculate the primary impedances, with the secondary leads calculated one way I got a primary impedance of 9 point something Kohms, calculating with them the other way I got an impedance of 5 point something Kohms or roughly 2.5 Kohms or so across each side of the CT of the OT. I think that reading is a little too high for a pair of 6L6s in this amp. Where the original LPTT got it's bark from was the 5U4s and the output tubes loading into that 4 ohm loaded OT. The tubes ran MUCH hotter than what they do in this amp. I have had experience with original LPTT amps and, like you say, set up correctly they will blow you out of the room set on 4 at the volume. The first thing I am doing is getting this Heyboer replacement one off transformer after the first of the year, see what that does, then start looking for the right OT. It WILL bark when I get it right, I promise. The new part number from Heyboer for this particular PT is - HTS-7281-2B and he priced it to me, one off single item for $150. Maybe we can locate a few guys to go in on a run of them. At a lot of 10 PTs the price drops to $120 each. Even if I can't find enough for an order of 10 I am springing for one myself in a month or so.

[dvlsadvc8t]

Hey avguy, I never got a notification of your response on this. I'll have to come back over and check in on this. Did you ever order the custom Heyboer? I've had no fun at all with mine. I contacted Mercury Magnetics about the transformer and was assured by the person there that the MM FTLPT-P/240 transformer was the correct one to get that would have 6A running to the rectifier tubes. Plus, I was even assured that it would fit the chasis and that it was made specifically for this chasis. Well, both of those assurances turned out to be incorrect. Not only does this power transformer run only 3A to the rectifiers, but it is also 1/4" to big for the chasis. I found this out tonight when I got the new PT, OT, and choke in from MM. Sadly for them, I get to call them up tomorrow and ask them why they fed me a bunch of crap when I asked specific questions regarding the PT. Now all of the parts are going back. I'll stick with the Mojo OT and choke for now and get the custom Heyboer PT. I'm not sure that I trust MM about the OT and choke now. This has become a ridiculous ordeal to go through for an amp.

[avguy49]

No, I haven't ordered the Heyboer as of yet. I sat down and composed an email and sent it to my Mojo contact regarding all of this. He and I have had multiple email conversations about this kit build over the last year. They keep insisting that somehow something must be mechanically wrong with the amp, IE a short, mis-wiring, etc. I explained about the Heyboer tranny in the email and told him how this is really really giving me second thoughts about the Mojo kits and not leaving me with a rosy feeling about going forward with other builds since I have several rather well known players wanting me to build amps for them this year. He wrote back and explained that he was sorry that I was having such a hard time with this kit and that he's heard this particular kit and how great it was and bla bla bla. Then he said he would offer me this; he said to pack up the wired chassis sans cabinet and ship it back to them and they would go through it with a fine tooth comb and if something was wrong they would fix it completely free of charge and ship it back to me. I really think I am going to do that because, here's the kicker, I have built amps for over 30 years and have a wealth of experience at this game. This particular amp I have traced down connection by connection completely from one end to the other no less than a dozen times at least and found nothing. The other thing is that several times now I have gone by the original Fender 5E8A schematic point by point checking all of the voltages completely and ALL of them are within spec. The other strange thing to me about all this is that this PT, under load with signal going through it is holding the 5V and 6.3V voltages just fine. The PT B+ voltage at the OP plates sags just about how I would expect it to for the TTLP amp. SO, the sum total of all this is even with 30+ years experience doing this I am not quite sure what the hell is going on with this amp but I am beginning to think that I have been barking up the wrong tree all along and that the issue may actually be in the OT and not the PT. BUT, I think that I am going to take them up on their offer and send it back to them and see what happens from there. This is REALLY bugging me because this should actually be a relatively simple build. It isn't that complicated and this isn't rocket science or voodoo that we're doing here it's just building a relatively simple tweed amp. We will see what happens I guess, but Heyboer does have that transformer available for $150 a unit and that is a good thing to know if I cannot get satisfaction with this deal through Mojo.

[dvlsadvc8t]

I was checking out some stuff last night for about 3 hours. I found a website where a guy documented a rebuild of an original '57 Low Power Tweed Twin. The PT originally in that amp is the Triad 7993 which is the same PT that was in the high power tweed twin. Even the MM website shows that their HPTT PT is the equivalent of the 7993. If the MM PT and Mojo's HPTT PT are pretty much the same then the PTs that we have with the LPTT are incorrect. At one point the Tweed Bassman did have the same PT as the LPTT. That transformer was the Triad 7993. I guess that during the schematic changes for the Bassman, a weaker PT was eventually used. Seems like for some reason, people thought it was a brilliant idea to have the LPTT follow suit. I fully believe that the PT is the #1 issue. There simply isn't enough amps running to the rectifiers. I am going to call Heyboer and order the PT. I also ordered a Weber copper cap last night to at least hold me over until the new tranny is completed. I'll let you know how the new tranny (as well as the copper cap) works as soon as I get it.

[avguy49]

If you are talking about that rebuild laid out on Ampmonster.com, I have seen that one. I think you are correct about the PTs. I am so irritated with this scenario, it just pisses me off. Between the anemic response of the completed kit, the OT schematic's color codes being all wrong, the endless emails with Mojo about this deal, and the responses pretty much telling me that I don't know ****** about what I am doing, I am going to explode like a Spinal Tap drummer. I may order that PT too in the next couple weeks, but for now I need to just set it aside for a while before I get the notion to give someone a Tony Lama Colonoscopy.....

[PokeyPete]

Very interesting thread! I would like to hear the updates from the last posts.
I just emailed Heyboer about the transformer to get the latest info and price.

[SoK66]

Look over on FDP and the 5E8A build thread in "Amp Mods...." The poster used a MOJO752 that has a heater center tap and says it's worked beautifully.