[TenTec] 255 Power Supply

[Jim Anderson]

After searching Google on how to test a transistor I realized I was doing it
wrong.

Here are the new readings...

On the Diode function and the black lead on the base it reads .514 on one
terminal and .000 on the other
With the red lead on the base it reads OL on one terminal and .000 on the
other.
Both transistors give the same results.

On the 2K ohm scale with the red lead on the base it reads 1.2 on one
terminal and .000 on the other
With the black lead on the base it reads 1.1 on one terminal and .000 on the
other.
Again, both transistors give the same results.

Thanks for sticking with me on this.

Jim

On Sat, Mar 12, 2011 at 7:39 PM, Jim Anderson <ural.jim at gmail.com> wrote:

> With the meter on Diode I get .513 in one direction and Open in the other.
> If I set the meter on the 2K ohm scale I get 1.18 but when I reverse the
> leads I get 1.2. Both transistors read the same.
>
> Jim
>
>
> On Sat, Mar 12, 2011 at 7:20 PM, Dr. Gerald N. Johnson <
> geraldj at weather.net> wrote:
>
>> Check the paralleled transistor junctions with an ohmmeter. The should
>> be a difference in directions and not zero ohms. The symptoms are that
>> the junction in at least one of the transistors is melted and so shorted.
>>
>> And it might be that the crowbar SCR has shorted.
>>
>> 73, Jerry, K0CQ
>>
>> On 3/12/2011 9:11 PM, Jim Anderson wrote:
>> > Thanks, I have done a bit more digging since I posted.
>> >
>> > If I pull the wire that leads from the diode bridge to the board with
>> the
>> > pass transistors no fuse blows. If I pull the internal 20 amp fuse and
>> turn
>> > it on the AC fuse is OK. If I disconnect the three wire plug that leads
>> from
>> > the transistor board to the regulator board it wants to blow the AC
>> fuse.
>> > So, as Al said, it seems to be an issue with that board. Is there a way
>> to
>> > check the transistors with them mounted or should I just assume it is
>> one of
>> > them and order a couple of replacements.
>> >
>> > Thanks.
>> > Jim
>> > _______________________________________________
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>> > TenTec at contesting.com
>> > http://lists.contesting.com/mailman/listinfo/tentec
>> >
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>
>