HIWATT DR 504 50 Watt Amp

[CJ]

got a nice piece in for a repair job, no sound the guy say,

70's Hiwatt EL-34 guitar amp,

 

[CJ]

yes those are Partridge transformers,

and darn it, the output is still good, 

but we are going to find out as much about it as we can from a non destructive viewpoint, as we do not want to ruin the $3,000 vintage resale value and get ourselves a job folding napkins in Reicker's Institute for the Criminally Insane. 

 

[pucho812]

no sound? did you use the sound spray? you have to recharge those every so often like a refrigerator or hvac.

Let me guess, it's missing that one preamp  tube or is it not that simple?

 

[CJ]

yeah, probably the tube,

chassis>

 

[CJ]

...

 

[volker]

yes those are Partridge transformers,

and darn it, the output is still good, 

Ah, too bad! I already had high hopes when I read the thread title. Have you tried dropping it ;D.

Immaculate on the inside, always a joy to look at.

 

[CJ]

well, our prayers have been answered! while pulling back the sleeving on a primary wire to measure wire size, the wire snapped like a dry twig in a stiff desert wind,

this brittleness factor obviously means that the rest of the winds are questionable and therefore warrant a complete tear down in order that we might make this amplifier more dependable by replacing the 50 year old wire with modern materials,



edit: looking at the wire that came oiff, it is a different gauge and type, so somebody had tried a splice and that is why yhe wire popped so easy, so good thing we started poking around in there as it was a bad connection and might be the reason the amp had problems,

 

[CJ]

we had room to do the PRR method of transformer reverse engineering and received the following numbers for comparison with the tear down

1430 T Pri

94 T and 66 T for the secondary  so about 15:1 and 22:1

this makes it a 3.8K:8/16 ohm transformer or thereabouts

 

[Brian Roth]

Ah, too bad! I already had high hopes when I read the thread title. Have you tried dropping it ;D.

Immaculate on the inside, always a joy to look at.

A friend of mine down in Florida is a huge fan of vintage Hiwatt/Marshall amps, and has done homework to build reissues:

http://royalamps.com/home.html

Check out these pix!  Look at the "Royal JPP"  series for his version of a Hiwatt:

http://royalamps.com/photos.html

IMHO, Eric's construction is waaay tidier than Hiwatt, which I always thought was beautiful.

Bri

 

[CJ]

Thanks so much for the links!   

 

[CJ]

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