There Has to Be a Better Way.

[Kevin Kuehn]

That's quite the transformation you've accomplished there. Would love to see more close up pictures of the detailing.

[Winky Dink]

I'm figuring out a few things myself.

The set came with an 89 replacing a 78 as an IF or RF amp. I replaced it with a good 78, and that eliminated a loud hum.

Most B-C voltages were 30% higher than Philco specs. Rectifier was putting out 410 volts instead of the specified 300v. Switched in different used 80 and the output went down to 330v most tube voltages are reasonable.

Made my first foray into alignment. Spent hours trying to make the signal generator give an audible output before I determined that the connecting cable was defective. I adjusted each capacitor to obtain max noise (AM band only).

So now I have a usable radio with fair-to-poor AM reception and some extraneous noises.

Now I'm stuck on a couple of B-C voltage issues. Here's the latest test results:



I can't figure out why the voltage to the plate on 85 is so low. All components test OK, and I've even tried replacing the resistors 48 and 49 with new ones. Would it be worthwhile (or risky?) trying a lower resistance for the 99K resistor?



Full schematic:

https://picasaweb.google.com/lh/phot...eat=directlink

If you're interested at all, here's a small album detailing replacement of missing condenser cans:

https://picasaweb.google.com/coldrb/...eat=directlink

[old_coot88]

Originally Posted by Winky Dink

?...I can't figure out why the voltage to the plate on 85 is so low. All components test OK, and I've even tried replacing the resistors 48 and 49 with new ones. Would it be worthwhile (or risky?) trying a lower resistance for the 99K resistor?

What is the (plate) voltage with the 85 removed? Does it jump up to the full 267 volts? If it does, i would try this (with the tube re-installed):

Since the 99K is the plate load resistor, shunt the 32K that's in series with it. Try maybe a 22K, a 10K, then a full shunt. That'll raise the voltage without losing signal-voltage swing across the 99K. See if this improves volume any.

...I adjusted each capacitor to obtain max noise (AM band only).

Which capacitors did you adjust? The ones in the IF cans, or the ones in the front end?

full schematic:
https://picasaweb.google.com/lh/phot...eat=directlink

Link won't come up on my rig. But found the Riders on Nostalgiaair
http://www.nostalgiaair.org/PagesByM...2/M0013822.pdf

[Winky Dink]

The full voltage did show up with the 85 removed. I tried the series of shunts, but there was no discernible change in volume. I have pretty good volume already.

The alignment was to two caps each on 1st & 2nd IF transformers, then two caps each on the three RF transformers, then the single "oscillator series."

I checked the link to the schematic, and it seems OK. I'll put it here, anyway for easier reference even though the readability is marginal.



I'm puzzled with the grid voltages--more often than not I get appropriate values, but negative instead of positive or vice versa, and it seems to work fine. On the 42s here, however, the value seems to be way off. But it still works.