Hiwatt DR504

[C Moore]

Doing a cap job on our 1979 head. It calls for three 220uf 350V caps. Are the 220/384 caps from JJ a good replacement?
Thank You

OK, now I have another question. My schematic shows 3 diodes but I see 4 on the board. Do not know if you can see from my crappy, dark pictures, but there is one at the bias pot, and three down by the last cap in the row. The soldering in this area is not factory. Can anybody tell this beginner what he is looking at?
Someone asked about a dual PI. I only see one PI and my schematic only shows one. That is to say, within my abilities, that is how I see the PI situation. I could be wrong.
Thank You

[gldtp99]

The JJ 220uf/385V cans would be fine electrically (i've used them before in similar amp re-caps) but the JJ's are a smaller diameter (1-3/16 vs common 1-3/8 ) and so they don't fit the existing clamps and chassis holes.
I'd use these F&T cans: http://www.vintagehiwattrestorations.co ... ducts_id=5

They're exactly what's called for and F&T are top quality..............gldtp99

[C Moore]

gldtp99 -
Thanks for the link. I have been real happy with F&T in our Fenders. I realize the JJ's have a smaller diameter (3/16 maybe?) than what is called for. There sure is a big price difference for those 220/385 caps though. Is it because F&T are the only company making that value in 1 3/8" diameter. I need three of them, and at $18.00 a piece... Is this one of those times you just have to grin and bare it? I could shim the JJ caps without much effort. But perhaps the F&T is worth the extra money?
Appreciate The Help

[skyboltone]

Doing a cap job on our 1979 head. It calls for three 220uf 350V caps. Are the 220/384 caps from JJ a good replacement?
Thank You

Could you post a couple of gut shots of the 504? I've always heard they are built like the brick schmidt house. Also the two tube PI puzzles.

[gldtp99]

If those F&T's are too expensive then another option are these CDE's from Mouser--- i've used these in DR504 clones-- just be sure to order the 1-38" (35mm) diameter cans: http://www.mouser.com/Search/Refine.asp ... 5-450v220a
You can also use 100/100uF@500V cans from JJ, etc------ just connect the two 100uF sections in parallel and you have a 200uF/500V can----these cans are 1-3/8" dia (35mm) and fit the existing clamps perfectly.
Classic Hiwatts don't have dual PI tubes---- the earlier circuits usually use 12at7 and the later circuits use 12ax7, but only one PI tube at a time.
Now the unusual Sound City SMF (150 watts EL34x8) uses two of the eight EL34's for PI duty--- six EL34's are outputs--- but this design has nothing to do with Hiwatt.....................gldtp99

[skyboltone]

If those F&T's are too expensive then another option are these CDE's from Mouser--- i've used these in DR504 clones-- just be sure to order the 1-38" (35mm) diameter cans: http://www.mouser.com/Search/Refine.asp ... 5-450v220a
You can also use 100/100uF@500V cans from JJ, etc------ just connect the two 100uF sections in parallel and you have a 200uF/500V can----these cans are 1-3/8" dia (35mm) and fit the existing clamps perfectly.
Classic Hiwatts don't have dual PI tubes---- the earlier circuits usually use 12at7 and the later circuits use 12ax7, but only one PI tube at a time.
Now the unusual Sound City SMF (150 watts EL34x8) uses two of the eight EL34's for PI duty--- six EL34's are outputs--- but this design has nothing to do with Hiwatt.....................gldtp99

I have a hand drawn schematic that I glanced at. I'll look again. It doesn't look much like a LTP on first examination but I'm often impatient and frequently wrong.

[gldtp99]

Mother lode of Hiwatt info: http://mhuss.com/Hiwatt/tech2.html

[skyboltone]

This is what threw (throwed?) me. V3 is the phase inverter. V4 an additional gain stage made necessary by the less than unity gain of V3. If I read this right NFB is added both at the PI and again at the last gain stage. The MV before the 0 gain PI is interesting too. Technically this is a single tube PI but without the final 12AX7 it wouldn't be much of an amp I fear. A pretty piece of work. I'll bet this bit accounts for most of the Hi-Watt lauded cleans. Anyway, thanks for the clarification and the great site from Mr Huss.
[img1400]http://mhuss.com/Hiwatt/Schematics/DR_Pre2Input.gif[/img]

[C Moore]

If those F&T's are too expensive then another option are these CDE's from Mouser--- i've used these in DR504 clones-- just be sure to order the 1-38" (35mm) diameter cans: http://www.mouser.com/Search/Refine.asp ... 5-450v220a
You can also use 100/100uF@500V cans from JJ, etc------ just connect the two 100uF sections in parallel and you have a 200uF/500V can----these cans are 1-3/8" dia (35mm) and fit the existing clamps perfectly.
Classic Hiwatts don't have dual PI tubes---- the earlier circuits usually use 12at7 and the later circuits use 12ax7, but only one PI tube at a time.
Now the unusual Sound City SMF (150 watts EL34x8) uses two of the eight EL34's for PI duty--- six EL34's are outputs--- but this design has nothing to do with Hiwatt.....................gldtp99

Hey, Thanks Again -
I went ahead and ordered those from Mouser. They do not carry multi-value caps (I called them) so I will get the 50-50 and the 32-32 (no 16-32) from CE Dist.
Anybody want to take a shot at my diode problem? (I edited my original post) My knowledge of electronics is novice at best, SS devices escape me completely. But what I was saying is that my schematic shows 3 diodes and I have 4. Is it possible somebody ran 2 diodes in series to equate a diode that was not available? Hopefully my pictures are clear enough to see what I am talking about. I can try to take some better photos...
Thank You

[gldtp99]

Sounds like you've got the Power Supply cans figured out--- i'd also get a new Bias capacitor--- it's an important part of a re-cap job---i usually use Sprauge Atom 100uF/100V caps in amps like this but a Xicon (or equiv) 100uF/100V or 100uF/63V will work ok---make sure to install the bias cap with the Pos end to ground.
Now for the Rectifier diodes---- somebody did a hack job on the rectifier diodes---- why they put two diodes in series on one side and a single diode on the other side is beyond me, who knows---- if this Hiwatt was on my bench i'd remove all rectifier diodes and install two new 1N5408 diodes (3A, 1000V)--- these 1N5408's are over rated for this job and would probably last until dinosaurs re-inhabit the earth, ie: no more rectifier problems, Ever......................gldtp99

PS--- i didn't really want to tackle this rectifier question because i was afraid of opening up a can of worms in this thread---- Freds, UF diodes, etc, etc ,etc------ the 1N5408 General Purpose Diodes will work incredibly well and are cheap insurance, IMHO--

[drew]

The soldering in this area is not factory.

You can say that again . . .

Can anybody tell this beginner what he is looking at?

I think the term you're looking for is "bodge."

What gldtp99 said - although Mhuss's power supply diagram http://mhuss.com/Hiwatt/Layouts/PowerAmpLayout50.gif suggests UF5408 rather than the 1N5408. The UF's are probably like 3 cents more expensive. It's a Hiwatt. Splurge. And when you put them in, make them look right! It's a Hiwatt!

[C Moore]

drew, gldtp99 -
Again, thank you. Good grief my memory is bad, I already took care of that bias cap (went with the suggested 100/100) when I added a bias pot. As for my diode "mystery"... thanks for shining a light in that regard. I will do as you guys suggested on all counts.
God I wish I were smarter. It takes me so long to get a rope around this electronics stuff. I just finished taking a class at my local college. It was a "Introduction To Electronics" type of course. I learned a lot and the teacher was first class, but we covered so much ground (the grob's basic electronics text) in such a short time period. The instructor did the best he could in the time he had. But that book could be the source of a two year degree all by itself IMHO. I'm the kind of guy that needs a lot of math and repetitious homework before things really sink in. I continue next semester with their digital course. So that's where I am at with this stuff...
Thanks Again, really appreciate it.
Chip

[C Moore]

http://www.mouser.com/Search/Refine.asp ... 5-450v220a

Not sure if I have ever used the "snap in" caps before. Is it OK to solder these connections?
Thanks

[Structo]

Can anybody tell me why some amps have a colored ink or something on top of the solder on these tag boards or turret boards?

Like in this HiWatt there is blue ink on the solder or on other amps you will see red ink?
Is that so you can tell if it has been altered after factory soldering?

[Structo]

http://www.mouser.com/Search/Refine.asp ... 5-450v220a

Not sure if I have ever used the "snap in" caps before. Is it OK to solder these connections?
Thanks

Those are made for PCB's.

You have to be careful when you order from Mouser because there are so many to choose from.

I've ordered stuff before and then when I got it I realized it was completely the wrong physical size component.

That particular cap is 1.38" in diameter if you didn't know.