Hi. No schematic for you but here's what I sort of know. All reasoning herein is shaky as it's based on your info and my defective understanding, so read it as guesswork & take care.
On the rectifier pin 6 has I reckon no internal connection so it's likely being used as a convenient solder point only. Any resistors coming off that are likely to be B+ voltage droppers for the plates of the tubes. You'll need a 5 watt possibly. Reason why it's burned out - shorted filter cap (that's the 16mfd) or maybe internally shorted 6X5, they were famous for this & sometimes took out the power tranny so check that too. If the value lies between 600 and 1600 ohms it's not that critical but if you're going to guess it I'd go high rather than low, then check the voltage it's putting through pin1 & make sure it's something the tube it goes to can take. What's pin 1 connected to? If it's the power valves then 350v or so would probably be ok; if it's the 6SJ7 150v would be quite a lot & for harp you want it lower anyway - 100v? At your own risk... but I'd try a 2K 5 watt first. The 6X5 is cheap, buy a new one before you do anything. Replace the cap too but don't go over 16mfd as the 6X5 won't like anything higher, that's its max for a first filter. And check the power tranny before that even. A Weber copper cap is available to replace the rectifier. Webervst.com.
Ok, about the 6V6s. Pin 1 I think is again not internally connected so is again likely being used as a solder tag only. This will therefore likely be a shared cathode resistor (esp if the pin 8s are connected to one another); it probably has a cap in parallel with it but maybe not. If it is a cathode resistor, this one you can vary to set the bias. 1500 ohms is likely to be (very) safely high (ie cold bias), and yes, it might go as low as 220. I'd use a 5 watt again to be on the safe side. Start high and work down till the bias is right.
Hope this helps your thinking.
Steve
Message: 24 Date: Sat, 18 Jun 2005 10:48:39 -0500 From: "Gary Bohannon" <beauxart2@xxxxxxxxxxx> Subject: [Harp-L] Dano Special Series D Model 68... schematic?
Just got one of these amps, made in '55 and in incredible shape. Looks like a 1x12" version of the 'Walter amp. It has tremelo and the following tube lineup:
6X5 rectifier 2x6V6GT power 6SJ7 12AX7 12AX7
When I got the amp and opened it up to change the filter caps/new cord etc, I noticed a small resistor across pins 6 and 8 of the rectifier tube... burned up beyond recognition. Tried to measure it and got readings anywhere from 1.6k ohms to around 600 ohms. I need to know what that resistor is. One of the pins, I think 8 (?) has a 16mfd X 450 volt cap tied to it.
The other burnt resistor is between the two power tubes and ties pin 8 of one tube and pin 1 of the other together. I looked inside my Silvertone 1432 (which has a similar tube lineup using a 6X5 rectier) and noticed that the resistor is 220 ohm... but no resistor across the rectifier tube... rats! So I think I'm halfway there...
Any help, or a schematic, would be appreciated.
Thanks in advance!
Gary B. Nashville