Partridge TG 6556/2 Output Transformer

we are going to rewind the coil using the same buried splice method as the original,

using 7 Nomex instead of 10 PB , this saves 6 mil since we use 2 pieces, and the paper sits a little flatter,

1 KV per mil = 7 KV of protection,

the turns compress the splice pretty flat, after the third layer of wire it is hard to notice much deformity in the coil so we are ok with doing all the splices like this,  and the pull out strength is very good compared to the taped lead method as there is tremendous pressure after all the turns are on, not as much so with outer layers but still pretty good,

we are hand winding this very slow as to keep the tension even for a tight build,  when you spin the wire on fast, there are lulls in winding tension due to the acceleration fluctuations of the wire,

if you wind really fast, you end up with a "sponge" as they call it, as the outward force tends to pull the wire away from the center line.

this is a unique coil in that they used a layered paper approach on a bobbin,  ie there are margins used on the sides of the wind as opposed to filling up the winding length all the way, 

on multiple winding machines, you can lay down the paper insl. off a big roll and slice the coils apart on a band saw, with bobbin winding, each piece has to be put down one at a time,

one advantage of the bobbin wind is that you eliminate the mistake of sawing a coil off center which can reduce margins and cause a short to the core,  this is the biggest Permali bobbin i have seen, probably very expensive, Permali has superior insulation properties over KP or Nylon.

first primary is down, looking over the start lead splice on the top >

all done with the rewind,  bake and dip, bolted it to the amp and it works fine, slight dip at 23 K Hz disappeared so now flat to 100 K,  sq wave looks the same,

#29 wire was a tight fit, Temco must have used a heavy build,  #30 would have been easier but would have higher DCR,  old wire was just a bit different, 

you could use 29.5 AWG if you could find it, Partridge  probably used metric wire, like 0.3 mm.

checking build as we get down to crunch time , and final assy>

made a mistake on lam thickness, it is not 006, but standard 29gaM6 (.0135"), we were comparing it to some .019" that came out of a Twin Reverb. 

but that is good news as that lam can be purchased from Edcor and Lamination Specialties without any hub bub,

print  changed to reflect lam  discovery,

Hi CJ, how are you? Very interesting and professional your work, congratulations! I build some amplifiers in Brazil and here it is very difficult to have access to faithful copies of transformers. Would you have the "recipe" for the Patridge TG5479/H6039K used in the DR103? I built one with a transformer but felt it sounded too loud. Thanks for now!

Hello,

Ooh, seeing this thread again refreshed the 'ole memory as I'd forgotten about this cracking thread about CJ's rewind of the Partridge Iron.

At a tangent I recently made a JTM50/Black Flag clone using early 70’s Sound City Partridge Mains and Output transformers. The metalwork, back/front panels, pots tag panel came from Modulus amps here in the UK, the rest was bits and pieces from the workshop salvage shelf/box.

It works OK, although I’ve yet to give it through bench test with the audio analyser, but the ‘ole amp came up fine using the sig gen and scope. I’ll probably voice it nearer the production 5F6.

Pics attached.

Terry

Nice work Thiago!

I have not done that Partridge model. Those guys are so rare 5hat they do not show up very often,

It might be the same coil structure ,

I am still waiting for a dead radio spares to show up but I do have a small Drake on the chopping block from a JTM 60.

valvepower said:

Olá,

Ooh, ver esse tópico novamente refrescou a velha memória, pois eu havia esquecido esse tópico sobre o retrocesso de CJ no Partridge Iron.

Em uma tangente, fiz recentemente um clone do JTM50/Black Flag usando transformadores de saída e alimentação Sound City Partridge do início dos anos 70. O trabalho em metal, painéis traseiros/frontais, painel de tags de potes veio de amplificadores Modulus aqui no Reino Unido, o resto foram pedaços da prateleira/caixa de salvamento da oficina.

Funciona bem, embora eu ainda não tenha feito um teste de bancada com o analisador de áudio, mas o 'ole amp funcionou bem usando o sig gen e o escopo. Provavelmente vou expressá-lo mais perto da produção 5F6.

Fotos em anexo.

terry

Click to expand...

Nice amp! Delicious transformers!

CJ said:

Belo trabalho Thiago!

Eu não fiz esse modelo Partridge. Esses caras são tão raros que não aparecem com muita frequência,

Pode ser a mesma estrutura de bobina,

Ainda estou esperando que um rádio sobressalente morto emocionalmente, mas tenho um pequeno Drake no bloco de corte de um JTM 60.

Click to expand...

I'm going to hope a lot for one day to appear and you rebuild an even better copy! I checked your work and it's a complete lesson for us! Thanks for sharing your findings.

Would it be possible to export transformers to Brazil?

Terry, in your clone in post #47, do you know if the PT and OT were from the same amp (it seems so), and was the choke also from that amp and does the choke have any markings? I have been collating Partridge model and batch number markings for a few years now as a way to date equipment, and also try and make sense of their marking scheme.

Thiago, many thanks for the nice words – it’s heartening to know the work is appreciated.

This amplifier is one of five JTM-5F6 clones with output powers ranging from 20 to 50 Watts with 6V6, KT66 and EL34 valves I’ve built over the last few years. I should get a group photo of them all together.

Tim, as far as I know both Partridge transformers came from the same Sound City 50 amplifier. I may see the chap I bought them from in a couple of month's time and I’ll ask him, however, I’m confident they came from the same amplifier. The choke came from a 1960’s Marshall 50 – I’ve had that choke for something like 40+ years, but can’t remember it’s exact history, but I think it came from a heavily modified total basket case amplifier.

I must go through the Partridge transformers I have here in the workshop and send the information to you – this goes back to a post on the UKVRRR forum from a little while back.

When I started work in 1975 building Roost guitar amplifiers, Roost [and Sound City] had already gone over to the Partridge clones made by Electrovoice transformers based in Rickmansworth, London. I remember the van delivering the transformers!

Electrovoice also supplied transformers for the Sterns Mullard 5-10 kits.

I remember seeing Partridge transformers in the early Roost [and Sound City amplifiers] that came in for repair.

The Sound City amplifier workshop was only a couple of miles across town from the Roost factory and I remember Sound City people occasionally popping by the Roost workshop. I often think I should have paid more attention to the finer detail of what was exactly is going on, but it was ‘just’ day to day stuff back then and wasn’t worthy of any detailed recording of the hows wheres and wherefores.

Terry.