Resistor across rectifying diode

Resistor across rectifying diode

Post by submmbo » Fri, 18 Apr 2008 16:23:51



Hello all

I've been working on an RCA RZS488D radio alarm clock lately. I just
had to replace the rotor w/ one I found on fleabay. This rotor did not
have the winding for the dial light, so I am investigating other ways
of powering it. In the process of seeing what power was available from
the power supply, I found a 220K, maybe 2W resistor in parallel with
the rectifying diode. The original rectifying diode was only marked w/
6EA. Since the schematic I had showed no such resistor I removed it
and at the same time installed a 1N4007 diode. The radio is currently
playing behind me. What might have that parallel resistor have been
for? I have never seen that type of setup as of yet.

On the subject of the dial light, the original was a #1490, 3.2V,
0.16A bulb. Without the extra winding in the clock motor, what would
be the best way to power this? There is a 36V DC source off the power
supply that I could step down. I would prefer that the light not be
very bright. Any ideas?

Thanks

Bob

 
 
 

Resistor across rectifying diode

Post by Ken » Fri, 18 Apr 2008 21:08:08


Quote:

> Hello all

> I've been working on an RCA RZS488D radio alarm clock lately. I just
> had to replace the rotor w/ one I found on fleabay. This rotor did not
> have the winding for the dial light, so I am investigating other ways
> of powering it. In the process of seeing what power was available from
> the power supply, I found a 220K, maybe 2W resistor in parallel with
> the rectifying diode. The original rectifying diode was only marked w/
> 6EA. Since the schematic I had showed no such resistor I removed it
> and at the same time installed a 1N4007 diode. The radio is currently
> playing behind me. What might have that parallel resistor have been
> for? I have never seen that type of setup as of yet.

> On the subject of the dial light, the original was a #1490, 3.2V,
> 0.16A bulb. Without the extra winding in the clock motor, what would
> be the best way to power this? There is a 36V DC source off the power
> supply that I could step down. I would prefer that the light not be
> very bright. Any ideas?

> Thanks

> Bob

Was the resistor original or tacked in, and what was the resistance?
What is the tube comp? You could use a small transformer for the pilot. Ken

 
 
 

Resistor across rectifying diode

Post by neses » Sat, 19 Apr 2008 00:23:44



Quote:
> Hello all

> I've been working on an RCA RZS488D radio alarm clock lately. I just
> had to replace the rotor w/ one I found on fleabay. This rotor did not
> have the winding for the dial light, so I am investigating other ways
> of powering it. In the process of seeing what power was available from
> the power supply, I found a 220K, maybe 2W resistor in parallel with
> the rectifying diode. The original rectifying diode was only marked w/
> 6EA. Since the schematic I had showed no such resistor I removed it
> and at the same time installed a 1N4007 diode. The radio is currently
> playing behind me. What might have that parallel resistor have been
> for? I have never seen that type of setup as of yet.

> On the subject of the dial light, the original was a #1490, 3.2V,
> 0.16A bulb. Without the extra winding in the clock motor, what would
> be the best way to power this? There is a 36V DC source off the power
> supply that I could step down. I would prefer that the light not be
> very bright. Any ideas?

> Thanks

> Bob

It could have been a capacitor [ceramic] across the diode. Thay can
come in a case similar to a resistor, but usually with one [or more]
more band[s] than a common resistor. That would be for diode noise
supression that can interfere with radio reception.

Is the winding for the clock motor exposed [ie. not two leads
disappearing into a sealed can]? If so, wrap 10 turns of fine
insulated wire around the coil and see what AC voltage you read across
it. For a 3.2V lamp you MAY not need all that many turns to power it.
Could it be effectively replaced with an LED?

Neil S.

 
 
 

Resistor across rectifying diode

Post by Mike Schult » Sat, 19 Apr 2008 04:21:51


Any idea how much current you can draw from the 36 vdc source?  There are 28
volt bulbs that draw about 60-70 ma.

--
Mike Schultz


Quote:
> Hello all

> I've been working on an RCA RZS488D radio alarm clock lately. I just
> had to replace the rotor w/ one I found on fleabay. This rotor did not
> have the winding for the dial light, so I am investigating other ways
> of powering it. In the process of seeing what power was available from
> the power supply, I found a 220K, maybe 2W resistor in parallel with
> the rectifying diode. The original rectifying diode was only marked w/
> 6EA. Since the schematic I had showed no such resistor I removed it
> and at the same time installed a 1N4007 diode. The radio is currently
> playing behind me. What might have that parallel resistor have been
> for? I have never seen that type of setup as of yet.

> On the subject of the dial light, the original was a #1490, 3.2V,
> 0.16A bulb. Without the extra winding in the clock motor, what would
> be the best way to power this? There is a 36V DC source off the power
> supply that I could step down. I would prefer that the light not be
> very bright. Any ideas?

> Thanks

> Bob

 
 
 

Resistor across rectifying diode

Post by submmbo » Mon, 21 Apr 2008 14:31:53


Managed to get distracted by an old computer I've been working on for
a few days in my spare time. Well the radio/alarm works and had been
waking me up the last couple of days. I just hate the cheap little
tiny things we have here at work. Most radios have a hard time in this
facility anyway. Although I already miss the light, as I have to turn
on the desk lamp to see what time it is.

The resistor in question was a 220K, maybe 2W or so. The soldering job
didn't look too factory, but it also had the same yellow spagetti
tubing on the leads as most of the rest of the unit, so I'm really not
sure about it being original or not. The radio uses transistors, no
tubes (sorry:), but since I am leaving this one at work, I decided to
opt for something that I wouldn't mind getting left on accidently if
someone else uses the room.

This is a General Time clock and the winding is on the back of the
rotor and covered w/ a wrapping, so I guess it might be possible to
try and mimic the original setup by use the fine wire wrapping.

The 36V source goes to the collector of the AF AMP transistor and the
base of the audio output transistor, but there is no indication on the
schematic for the current draw.

I think I could use an LED as a replacement and would welcome any
circuit ideas on this. The radio is not really a classic, just a
decent radio alarm that I'd like to keep going.