And another Paraglow question

[fitz]

Ok I am about half way complete on the Paraglow kit. I was running thru the parts and found the 2.5k and 3k 12 watt resistors. I also noticed a pair of 4k 12 watt resistors in the parts that I have. Is this a mistake or is this part of a design change ? I couldn't find anything in my manual about it. Maybe an easy way to run some 45 tubes ?

[Paul Birkeland]

I can't speak to the other values, but I would suggest replacing the 3K/12W resistor with a 3K/20+W resistor based on personal experience.  (The 12W will work, but it runs hot enough to discolor other parts around it, which can be visually annoying)

[Paul Joppa]

You'll have to remind me of what exactly you have. (Is there another thread with the details?) Specifically, do you have the Magnequest PGP8.1 power transformer? I ask because there were two transformers used with that amp, and they have different voltages and should use different operating points (and cathode resistors).

[fitz]

Yes i have the pgp 8.1 transformers.

[fitz]

Thanks for the tip Caucasian Blackplate. I have seen some Dale aluminum housed 25w resistors and some Ohmite 25w resistors. The Ohmites are the same construction as the stock ones in the kit, just higher wattage rating. Should I stick with the Ohmite brand or use the aluminum housed Dale resistors ?

[RPMac]

Fitz, the 2k5 resistors were for using a KR 2A3. For standard and NOS 2A3s, you will use the 3K resister. This being a direct coupled amp, PJ will need to know the driver tube. If you are building by the manual and stock(as you should and as Doc and PJ preach), you will be using half of the 5965 with a 274 cathode resister. The driver C4S has a top resister of 100 and the bottom paralleled 270K and 100K. The C4S B+ is sourced above the 2A3 cathode resister.

PB's suggestion is a good one, but wait until you have the amps up and running with the voltages worked out. PJ may want you to go with the 4K which will require other changes.

You WILL BE HAPPY when you are done!

[Paul Joppa]

OK, thanks. In that case, use the 3000 ohms. If you get bigger ones (recommended) I'd go with the Ohmite on the grounds it's a known quantity.

The 2500 is a good value for the deYoung power transformer, but I think very few Paraglows actually had that one. I have no idea why there's a 4K!

You may want to adjust the value of the 274 ohm cathode resistor under the 5965, in order to optimize the voltages. If you post the voltages (especially at the tube pins) once it's running, I'll help with that.

Be aware that the 100uF electrolytic capacitors are kind of old at this point, and are running near their rated maximum voltage. They will repair themselves under voltage, but are under heavy stress until that process is completed. It's possible one or two may fail - just a caution, with luck you won't need to know this...

[fitz]

Thanks for your help Paul. Yah the 4k 12watt resistor is a mystery to me. Once I get everything finished I will post the voltages on the driver tube. I was also wondering about the age of the capactitors and hoping I would get lucky on them. But after recent knee surgery and then a tire blowing out on the highway last weekend, its not looking like luck is on my side.

Hello RPMac. Yes I am building the kit per the manual. It is the original Paraglow I, not the upgraded II. Im not even interested in changing the parafeed cap at this time. I'm too interested to see how the Solen sounds.

Thanks to everyone for all the help with my "late to the party" questions.

[Doc B.]

IIRC the 4K was put in series with the 3K to bias a 45 tube.