Waiting on the new 5 watt metal film resistors to correct the
power supply resistors. (replacing the sand ohm and candelohm
resistors.) Still need to pu the 9.1 V zener across the 3V4
(B+) and ground to protect the filaments from over voltage.

Jeff

Jeffrey D Angus wrote:
Waiting on the new 5 watt metal film resistors to correct the
power supply resistors. (replacing the sand ohm and candelohm
resistors.) Still need to pu the 9.1 V zener across the 3V4
(B+) and ground to protect the filaments from over voltage.

I removed the 55/75 Ohm sand bar resistor and replaced it with
a 2500 ohm 50 watt Ohmite rheostat. I Temporarily soldered in
a 1N4007 diode being fed with the AC line voltage and fiddled
with the Ohmit variable to optimize the new resistance values.
Effectively, replace the 55 ohm portion with a 56 ohm 5 watt
metal film resistor, and the 75 ohm portion with a 120 ohm 5
watt metal ohm resistor. The candelohm dual 950 Ohm resistor
was open in both sections, so a 910 ohm 5 watt metal film
resistor for the first section and a 1.0 K ohm 5 watt metal
film resistor for the second section are on order.

Data sheet:
http://www.mouser.com/catalog/specsheets/XC-600044.pdf

The Zenith H500 TO appears to draw approximately 50 mA on the
filament string, and a total of about 75 mA on the B+ when the
volume is up about 2/3 of the way. (I used a Heathkit B+ supply
to directly feed the radio B+ with 106 vdc to measure the current.)

Side note: All the caps were replaced as if they were factory
originals. I.e., desoldered the original leads and removed them,
then reinstalled and soldered the new leads. No hook splices or
quiggs.

Jeff

"Jeffrey D Angus" wrote in message
...
Waiting on the new 5 watt metal film resistors to correct the
power supply resistors. (replacing the sand ohm and candelohm
resistors.) Still need to pu the 9.1 V zener across the 3V4
(B+) and ground to protect the filaments from over voltage.

Jeff

Looks nice. I did a similar thing to my H500.

I don't recall exactly, but isn't that cap in the lower left corner across
the AC line? If so, it should be a type X (IIRC) cap an not a regular paper
cap.

Barry - N4BUQ

Barry wrote:
I don't recall exactly, but isn't that cap in the lower left corner across
the AC line? If so, it should be a type X (IIRC) cap an not a regular paper
cap.

It should, but it's a 630 vdc new mylar cap. I'm waiting on an
order of those to come in.

Jeff

Ah, yes. The familiar solder spool chassis prop.

--
Jim Mueller

To get my real email address, replace wrongname with eportiz. Then replace
nospam with sacbeemail.

"Jeffrey D Angus" wrote in message
...
Waiting on the new 5 watt metal film resistors to correct the
power supply resistors. (replacing the sand ohm and candelohm
resistors.) Still need to pu the 9.1 V zener across the 3V4
(B+) and ground to protect the filaments from over voltage.

Jeff

Jim Mueller wrote:
Ah, yes. The familiar solder spool chassis prop.

Along with several little block of wood or what ever else
is at hand at the time. Certainly a lot cheaper than buying
a frame that is of questionable usability most of the time.

Jeff

And now, the shiny new electrolytic capacitors.

220 uF @ 25 v, 2 each 22 uF @ 160 v, 47 uF @ 160 v and a
pair of 33 uF @ 160 v to replace the original 60 uF.

The terminal strips hold them and the new 5 watt resistors
that are on order.

Jeff

How did those old style 20% carbons check out? (Particularly
the ones with the rougher finish on the bakelite shell...) I usually
find many of them open or way high in value.

Pete

"Jeffrey D Angus" wrote in message
...
Waiting on the new 5 watt metal film resistors to correct the
power supply resistors. (replacing the sand ohm and candelohm
resistors.) Still need to pu the 9.1 V zener across the 3V4
(B+) and ground to protect the filaments from over voltage.

Jeff

Tio Pedro wrote:
How did those old style 20% carbons check out? (Particularly
the ones with the rougher finish on the bakelite shell...) I usually
find many of them open or way high in value.

Surprisingly enough, I haven't had any problems with them.
What did die was the 950/950 Candelohm bolted to the chassis
and of course, the original sand-ohm 55/75 resister had a
case of seriously green leads.

Jeff

"Jeffrey D Angus" wrote in message
...
Tio Pedro wrote:
How did those old style 20% carbons check out? (Particularly
the ones with the rougher finish on the bakelite shell...) I usually
find many of them open or way high in value.

Surprisingly enough, I haven't had any problems with them.
What did die was the 950/950 Candelohm bolted to the chassis
and of course, the original sand-ohm 55/75 resister had a
case of seriously green leads.

Jeff

Oddly enough, I'm finding yellow mylars with the same greenie
lead disease. One flex, and the lead is gone.