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RV power converter Todd PC40 -- insulator problem

M

Michael Caplan

Jan 1, 1970
0
Does anyone have information on or experience with the PC40, 40 amp
converter made by Todd Engineering Sales of Tucson (now out of business)?
I'd sure like to get hold of a schematic, but my main interest right now is
in identifying the special insulator used under the mosfets.

The power supply is used to provide the 12 DC used in recreational travel
trailers.

It's basically three paralleled SMPS's mounted inside a large aluminum heat
sink (which is also the case), one of which, as far as I can tell, is the
master.

The unit came into my shop with no output. After getting the case opened
(it's all pop-riveted) and pulling out the master board, I found the IRF740
mosfet on this board shorted and the resistor next to it open (looks like
0.24 Ohms, 2 Watt -- red, yellow, silver, then gold on a gray body). I
also found signs of arcing from the mosfet to the heat sink. The arcing
appears to have been through the mosfet's insulator, and that is where I am
puzzled.

The mosfet, an IRF740 in a TO-220 type case, is insulated from the heat sink
by a piece of what at first looks like a standard silicon rubber heat
conductive insulator. However, I was attracted to the fact that there is a
grounding wire soldered to the insulator. On much closer examination I
confirmed that the insulator has a metallic core ("middle of the sandwich").
The point where the heat sink was marked by the arcing corresponds to the
narrow edge of the insulator where the metallic core is now exposed.

I suspect that the insulator is compromised and should not be reused. But I
haven't seen this type of insulation material before and was wondering if
anyone has come across it. Is there a description and trade name for it?
What about sources?

Michael Caplan CET
 
T

Tony Marsillo

Jan 1, 1970
0
Mike,
I am working on the same unit. I am trying to find out the part number of U2
on the main PCB. It is a 3 terminal TO-92 plastic device, it burned up and I
can not read the markings.. My unit has a standard insulator, no wire
soldered to it. The main board near the large chassis terminal has a spade
terminal soldered to the PCB and held in contact with the heatsink with a
clip. Also do you know if the telephone type connector is required to turn
the unit on.

Thanks
 

Marshcollins

Sep 5, 2009
1
Joined
Sep 5, 2009
Messages
1
PC40 phone connector

I have a manual for the PC40 which indicates the phone connector is for a jumper which switches the voltage from 14.1 vdc output to a lower voltage for when you are continuously connected to shore power. Higher voltage with the jumper installed.
 

timotb

Oct 29, 2009
2
Joined
Oct 29, 2009
Messages
2
Todd PC30 Charger

Could someone tell me if I can use the Todd 12 volt 30 amp model PC30 as a full time battery maintainer. Does this unit have the circuitry to shut off and not over charge a battery if always plugged in and connected?
 

Reitan

May 5, 2010
2
Joined
May 5, 2010
Messages
2
Todd Engineering Sales, Inc. Model PC 40 Power Source

Sirs,

I have successfully repaired a Todd Engineering Sales, Inc. Model PC 40 power source. I drew a schmatic diagram and I would be delighted to share that with those of you that would like to have one.

I found two open 62K ohm resistors that are in parallel in the zener voltage regulator circuit that powers the PWM IC circuit. Also a N channel power MESH MOSFET was bad in one of the PC boards.

In exchange I am searching for a schmatic diagram to a Todd Engineering Sales, Inc. power source battery charger/ power supply, model PC30B.

I hope this will be of some help.

Rodney
 

Reitan

May 5, 2010
2
Joined
May 5, 2010
Messages
2
Mike,
I am working on the same unit. I am trying to find out the part number of U2
on the main PCB. It is a 3 terminal TO-92 plastic device, it burned up and I
can not read the markings.. My unit has a standard insulator, no wire
soldered to it. The main board near the large chassis terminal has a spade
terminal soldered to the PCB and held in contact with the heatsink with a
clip. Also do you know if the telephone type connector is required to turn
the unit on.

Thanks

--
Tony Marsillo
Nutmeg Repair
-----------------------------------------------------------------
"Michael Caplan" <[email protected]> wrote in message
news:[email protected]...
> Does anyone have information on or experience with the PC40, 40 amp
> converter made by Todd Engineering Sales of Tucson (now out of business)?
> I'd sure like to get hold of a schematic, but my main interest right now

is
> in identifying the special insulator used under the mosfets.
>
> The power supply is used to provide the 12 DC used in recreational travel
> trailers.
>
> It's basically three paralleled SMPS's mounted inside a large aluminum

heat
> sink (which is also the case), one of which, as far as I can tell, is the
> master.
>
> The unit came into my shop with no output. After getting the case opened
> (it's all pop-riveted) and pulling out the master board, I found the

IRF740
> mosfet on this board shorted and the resistor next to it open (looks like
> 0.24 Ohms, 2 Watt -- red, yellow, silver, then gold on a gray body). I
> also found signs of arcing from the mosfet to the heat sink. The arcing
> appears to have been through the mosfet's insulator, and that is where I

am
> puzzled.
>
> The mosfet, an IRF740 in a TO-220 type case, is insulated from the heat

sink
> by a piece of what at first looks like a standard silicon rubber heat
> conductive insulator. However, I was attracted to the fact that there is

a
> grounding wire soldered to the insulator. On much closer examination I
> confirmed that the insulator has a metallic core ("middle of the

sandwich").
> The point where the heat sink was marked by the arcing corresponds to the
> narrow edge of the insulator where the metallic core is now exposed.
>
> I suspect that the insulator is compromised and should not be reused. But

I
> haven't seen this type of insulation material before and was wondering if
> anyone has come across it. Is there a description and trade name for it?
> What about sources?
>
> Michael Caplan CET
>
>
Sir.

I has repaired this power supply and I may have some answers to your questions. Please feel free to contact me.

Rodney
 

pomonabill220

Jun 8, 2010
2
Joined
Jun 8, 2010
Messages
2
Mike,
I am working on the same unit. I am trying to find out the part number of U2
on the main PCB. It is a 3 terminal TO-92 plastic device, it burned up and I
can not read the markings.. My unit has a standard insulator, no wire
soldered to it. The main board near the large chassis terminal has a spade
terminal soldered to the PCB and held in contact with the heatsink with a
clip. Also do you know if the telephone type connector is required to turn
the unit on.

Thanks

--
Tony Marsillo
Nutmeg Repair
-----------------------------------------------------------------
"Michael Caplan" <[email protected]> wrote in message
news:[email protected]...
> Does anyone have information on or experience with the PC40, 40 amp
> converter made by Todd Engineering Sales of Tucson (now out of business)?
> I'd sure like to get hold of a schematic, but my main interest right now

is
> in identifying the special insulator used under the mosfets.
>
> The power supply is used to provide the 12 DC used in recreational travel
> trailers.
>
> It's basically three paralleled SMPS's mounted inside a large aluminum

heat
> sink (which is also the case), one of which, as far as I can tell, is the
> master.
>
> The unit came into my shop with no output. After getting the case opened
> (it's all pop-riveted) and pulling out the master board, I found the

IRF740
> mosfet on this board shorted and the resistor next to it open (looks like
> 0.24 Ohms, 2 Watt -- red, yellow, silver, then gold on a gray body). I
> also found signs of arcing from the mosfet to the heat sink. The arcing
> appears to have been through the mosfet's insulator, and that is where I

am
> puzzled.
>
> The mosfet, an IRF740 in a TO-220 type case, is insulated from the heat

sink
> by a piece of what at first looks like a standard silicon rubber heat
> conductive insulator. However, I was attracted to the fact that there is

a
> grounding wire soldered to the insulator. On much closer examination I
> confirmed that the insulator has a metallic core ("middle of the

sandwich").
> The point where the heat sink was marked by the arcing corresponds to the
> narrow edge of the insulator where the metallic core is now exposed.
>
> I suspect that the insulator is compromised and should not be reused. But

I
> haven't seen this type of insulation material before and was wondering if
> anyone has come across it. Is there a description and trade name for it?
> What about sources?
>
> Michael Caplan CET
>
>
Hello Tony;
I have a PC30E that my father gave to me (not working... BIG inductor got REAL hot and chared the pcboard) BUT my U2 (a T0-92 package) has SiLR 645 stamped on it. Also, the board is labeled U2 RT2 OT. NOTE also that right next to this device is a long rectangular (about 1/2 inch tall) mechanical thermostat, THAT might be the RT2 OT NOT the SiLR 645,,,, so take note! So it might be a solid state temperature sensor. All three leads are used (traces).
I hope this helps.
IF you have a schematic for the PC30E, I would appreciate seeing your work!
Thanks!
 
Last edited:

lambiasow

Jun 30, 2010
1
Joined
Jun 30, 2010
Messages
1
Does the manual include a schematic?

can you post the manual to this site?

Bill


I have a manual for the PC40 which indicates the phone connector is for a jumper which switches the voltage from 14.1 vdc output to a lower voltage for when you are continuously connected to shore power. Higher voltage with the jumper installed.
 

pomonabill220

Jun 8, 2010
2
Joined
Jun 8, 2010
Messages
2
U2 (the TO-92 package) is a "smps startup regulator". It has a max input of 450volts and output of 15 volts for the switcher drive. After the supply starts, a winding on the transformer is used to supply the logic and the U2 is shutoff. The logic supply uses a power resistor to limit current, a diode to rectify and a zener to regulate the 15 volts. My supply had a bad LM393 (dual comparitor) as well, but it would still run. The comparitor is probably used to current limit, or overcurrent protection, or just for voltage selection... havent found out yet.
It also appears that the mechanical thermostat is for over temp, and the comparitor shuts down the supply if it gets too hot (yeah right!), or turns the fan on. Just a guess as I learn more.
over temp is kind of a joke... why did the output inductor in mine cook the board and melt the tape wrapped around it then?!?!?! I got mine with the fan frozen!
 
Last edited:

berger316

Jul 7, 2010
1
Joined
Jul 7, 2010
Messages
1
Reitan,

I am also having issues with my PC40 unit.
Could you send me a copy of your schematic.

Thanks.
 

icabod2

Jul 8, 2010
1
Joined
Jul 8, 2010
Messages
1
I would love a copy of your schematic please. I have a model PC 45 which I am sure must be similar.
 

ROMOAS

Sep 28, 2010
1
Joined
Sep 28, 2010
Messages
1
please send me a sch and a parts list i have all the parts i need but 2 items i can not identify mine fryed big time but the transformers are ok so i'm just repairing it for fun i have the PC40 thank you [email protected]
 

linetrash75

Oct 20, 2010
2
Joined
Oct 20, 2010
Messages
2
I have a todd engineering PC40 that is not working, the most i,am capable of is checking in ternal fuse. CZould somebody walk me though this or possibly fix it if i shipp it to you.

Thanks Jed
 
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