Harry Joyce amp gut shots?

[Roe]

Interesting... so my schematic might not be fully correct then?

I based it on the two 50 watt models found on this website :
https://hiwatt.org/ipage.php?n=13

This one as well:
https://ampgarage.com/forum/viewtopic.p ... 38c7603215

I don't know really. But a 1k5 would reduce the gain greatly and cut some bass. however there are plenty of gainstages in this amp so perhaps it is not a problem

[Emiel]

Interesting... so my schematic might not be fully correct then?

I based it on the two 50 watt models found on this website :
https://hiwatt.org/ipage.php?n=13

This one as well:
https://ampgarage.com/forum/viewtopic.p ... 38c7603215

I don't know really. But a 1k5 would reduce the gain greatly and cut some bass. however there are plenty of gainstages in this amp so perhaps it is not a problem

Well, the 1K5 resistor is part of the cascading gain stage on V2, which a regular Hiwatt DR lacks altogether...

[JD0x0]

On paper, that'd have like no gain and even less bass.

Honestly, no reason not to run a trimmer there, and adjust the coupler to keep a similar bass cutoff to the original circuits. The OL amps had a pot labeled 'Overdrive' I believe 500k, but a 100k would probably be better suited to the Hiwatt vibe, unless you're looking for a good bit of gain and distortion on tap. Also, personally, not a fan of the 47nF cathode bypass caps.

There is an extra gainstage on V2 (resistor and capacitor). I'd say there is just a little bit more gain in my amp compared to a regular DR103.

That doesn't really matter. With the 1.5k grid leak you have a gain factor of .04 @ 1khz and .02@ 80hz. For reference, a 220k grid leak would give you a gain factor of .85 @ 1khz. .04 is like no signal, it doesn't matter there's an additional gain stage, because it's getting almost no signal to 'recover'

Are you sure that's not like a 15K there, or something instead of the 1k5? Stock value was 47k IIRC.


FWIW, you can check the 'OL' schematics. Those have the 'extra' gain stage too. They don't have a 1k5 grid leak between those stages. I'm 99.9% sure that's a mistake. I have an amp with 4 cascading gain stages, and if you turned the OD trim to '0' that'd give you 1k grid leak resistance. It didn't even perceivably pass signal with a value that low and that amp has a TON more gain than a hiwatt, even with the 'extra' stage. Sorry, I'm not buying that value, there..

[Emiel]

A 1K5 resistor has the color codes brown-green-red-gold. You can find the same resistor on the V1 cathodes.

Here are pictures of two HJ 50 watters. In both amps the said resistors have black dots on the brown stripe but to me it reads brown-green-red-gold. 15k would be brown-green-orange-gold.

What do you think?

HJ 50 #1


HJ 50 #2


HJ 50 #2 pic from another angle

[Emiel]

A kind fellow sent me pictures of his later HJ, including this one.

What do you reckon?

[Emiel]

Bumping this one.

Any thoughts on the value of the resistor on V2?

[Emiel]

For those interested.

In the end, we upped the resistor to 15K. The result was much more overdrive. Because there was a lack in low end, we decided to remove the resistor and capacitor all together. And the low end is all there now. Makes you wonder why Harry Joyce needed to cut low end, maybe because of the transformers used?

[h4x0r]

What's with the prussian blue over everything? Tamper tell-tale? or QC?

[drew]

What's with the prussian blue over everything? Tamper tell-tale? or QC?

https://www.harry-joyce.com/hjmilspc.htm

[Emiel]

What's with the prussian blue over everything? Tamper tell-tale? or QC?

The Harry Joyce website is down, but I'm pretty sure it's for QC, plus it tells whether someone else has tampered with the connections.