found a chassis in my storage place :D

[norburybrook]

4u7 in the recovery stage cathode would roll off some low frequency. Power supply should be like this. 3W is overkill for those two resistors. They could both be as small as 1/2W.

Martin are you saying the 22k should be changed to a 47K? I've put a 100k in already on the 2k2 spot.

I've had to order a pack of 10 47uf's


M

[martin manning]

Martin are you saying the 22k should be changed to a 47K? I've put a 100k in already on the 2k2 spot.

I've had to order a pack of 10 47uf's

That'd be my guess. If your screen voltage is 450, you need to drop 100V with say 2.2 mA. Don't worry, parts are cheaper in lots of 10, and this isn't your last amp ;^)

[fred.violleau]

It would go like this, I believe.
Edit: The basic idea is the same, but I see the HRM w/ on-board loop layout has some non-standard values in the loop, and it's missing a couple of grounds.

Yeah per Martin's changes on Henry's layout, the 27 k instead of the 10k will get you in the 30v range. I had followed the same layout on my first build and ended up at 15v with the 10k tail resistor, makes a huge difference in the sound! I did not update the 1.5k to 1.8k though nor the bypass cap and think it still is 5uf 25v.

I do ground the loop at the FX loop jack and it works fine, no added hum the amp really quiet.

And @Tony, thanks for clarifying the serial, parralele options, because I am willing to add the parralele option on my last build and had seen this double pot setup, but did not know which was better.

Have to order that type of dual pot since I don't have these at hand..

Fred.

[fred.violleau]

Martin are you saying the 22k should be changed to a 47K? I've put a 100k in already on the 2k2 spot.

I've had to order a pack of 10 47uf's

That'd be my guess. If your screen voltage is 450, you need to drop 100V with say 2.2 mA. Don't worry, parts are cheaper in lots of 10, and this isn't your last amp ;^)

@Marcus, check on my last build the values for the B+ rail since you seem to position the d-lator same place I did. The first dropping string is 12k, for 450 volts

This is my schematic:

[martin manning]

Your loop dropping string is quite different, though, Fred.

[norburybrook]

Martin are you saying the 22k should be changed to a 47K? I've put a 100k in already on the 2k2 spot.

I've had to order a pack of 10 47uf's

That'd be my guess. If your screen voltage is 450, you need to drop 100V with say 2.2 mA. Don't worry, parts are cheaper in lots of 10, and this isn't your last amp ;^)

I think my screen voltage will be nearer 485 as I've gone for a 345-0-345 transformer as I'm going to use El34's

Will I still be in the ball park? Only issue I have is the PCB power board makes changing resistors difficult, the main board I made is eyelets so no problem there.

my transformers are arriving later this week so I'll be able to finish this weekend.


M

[martin manning]

I don’t see a problem, just adjust the first dropping resistor in the loop power supply branch to get 350-360V at B+3a. For the resistor value, (B+3 - 360)/0.0022 would be a good guess. If you have 485 B+3, I’d try something close to 57k. Erwin’s pcb is almost like an eyelet board, no?

[norburybrook]

I don’t see a problem, just adjust the first dropping resistor in the loop power supply branch to get 350-360V at B+3a. For the resistor value, (B+3 - 360)/0.0022 would be a good guess. If you have 485 B+3, I’d try something close to 57k. Erwin’s pcb is almost like an eyelet board, no?

Not for the components its a proper PCB small component hole onto traces thing. the main wire connection points are like eyelets.

M

[didit]

I don’t see a problem, just adjust the first dropping resistor in the loop power supply branch to get 350-360V at B+3a. For the resistor value, (B+3 - 360)/0.0022 would be a good guess. If you have 485 B+3, I’d try something close to 57k. Erwin’s pcb is almost like an eyelet board, no?

Not for the components its a proper PCB small component hole onto traces thing. the main wire connection points are like eyelets.

M

I've been successful soldering small gauge turrets or even pins with a socket onto PCB holes when easy changes are desired. Perhaps that'd work here? Temporarily of course.

Best .. Ian

[norburybrook]

I don’t see a problem, just adjust the first dropping resistor in the loop power supply branch to get 350-360V at B+3a. For the resistor value, (B+3 - 360)/0.0022 would be a good guess. If you have 485 B+3, I’d try something close to 57k. Erwin’s pcb is almost like an eyelet board, no?

Not for the components its a proper PCB small component hole onto traces thing. the main wire connection points are like eyelets.

M

I've been successful soldering small gauge turrets or even pins with a socket onto PCB holes when easy changes are desired. Perhaps that'd work here?

Best .. Ian

Ian, That's a good idea


Been busy playing music today so didn't get much done.

IMG_20191104_155320-01.jpeg

however my Snake Skin tolex is here...direct from China./...1/3 the price from Tube town

IMG_20191104_155712.jpg

IMG_20191104_155719.jpg

M

[didit]

Posting that photo of your D'Angelico makes for no sympathy, just envy.

[martin manning]

With plated-through holes you should be able to pull that resistor from the top (unless you bent the leads over underneath), then use your super solder sucker to clean out the holes.

[erwin_ve]

With plated-through holes you should be able to pull that resistor from the top (unless you bent the leads over underneath), then use your super solder sucker to clean out the holes.

Exactly! It is a plated through hole.

[norburybrook]

With plated-through holes you should be able to pull that resistor from the top (unless you bent the leads over underneath), then use your super solder sucker to clean out the holes.

yes, but because it was a 3w resistor the leads only just go through the hole tightly so it's hard to get them out.


I've got the 47k in there now, lets hope that stays


M


p.s. the boards are beautiful quality by the way. Erwin did a great job with these, really top notch

[martin manning]

BTW what’s the voltage rating on those caps in the loop power supply branch? Since they are not stacked like the preamp filters they should be rated for the unloaded B+ voltage.