Paraglow (2005) instructions and schematics needed..

[Doc B.]

I'm happy to help and send a copy of the manual for this long retired kit, however I would suggest that it's not very logical to challenge design choices and at the same time ask for help understanding how the circuit is laid out. There are updates that are more important than worrying about the carbon comp grid stoppers.  As long as you don't ham fist the stoppers when installing them they will work fine.

To make the amp as reliable as possible uprate the wattage of the cathode resistor as suggested and also use higher rated caps in the power supply, as the B+ can exceed the cap voltage rating in some situations and typically runs close enough to the limit that we have found those caps can fail after about ten years. We typically use two 270uF 350V rated caps in series with appropriate compensation resistors when we retrofit the original 100uF 450V caps in Paraglow and Parabee.

[Bluesman]

Doc, please don´t see it as a design challenge. I was just stumped there for a while, coming from a different world. No offense, please.

I´ll have a look at what caps and cathode resistors I have in stock here and take appropriate action.

Cheers /Richard

[Bluesman]

Well, after reading the manual and seeing the schematic, I am really impressed. That parafeed thing is new to me, along with the power stage driver system. Who would have thought that preamp tube is actually for computer applications (as per the datasheet). It´s going to be a fun ride.
Will be doing inventory later today, checking for the necessary upgrade components.
 

[Bluesman]

Couple of questions, though:
How have you guys mounted the little driver PCB in your chassis? Nylon standoffs?
Same goes for the hum balance pots, I feel like attaching them to something more than just the soldering points of a tube socket. Glueing the backside of the pots to the chassis plate, maybe?


 

 

[Grainger49]

I'd drill a hole and mount the hum pot through the top plate.  This is now standard for all Bottlehead kits with them.

[Bluesman]

Yup, That´s probably the way to do it. It clutters the top of the base somewhat, but makes things more sturdy and serviceable.

[Bluesman]

What about the driver PCB - would it be OK to glue a standoff to the bottom of the top plate (to avoid yet another hole), and mount the PCB on it via a screw?

And finally - regulations over here demand that the power switch breaks both incoming AC lines. Has anyone found a proper switch small enough to be pressed into the present power switch recess, or will I need to open it up for a larger switch?

[Paul Birkeland]

You won't find the space you need to mount the hum pots through the chassis plate in a reasonable manner, I would just solder them to the tube pins.  This is  part that is only adjusted when you swap tubes, which is pretty infrequent with 2A3's.

Once the amplifier is 100% functional, you can stand up the driver C4S board and silicone it to the top plate with two dots of silicone.

We do now use standoffs and hardware, but this kit is not setup for that.