wrote:
In sci.electronics.repair, on Fri, 13 Mar 2026 22:44:36 -0400, micky
<NONONOmisc07@fmguy.com> wrote:
>In sci.electronics.repair, on Thu, 12 Mar 2026 09:24:59 -0400, legg>
<legg@nospam.magma.ca> wrote:
>On Thu, 12 Mar 2026 01:00:56 -0400, micky <NONONOmisc07@fmguy.com>>
wrote:
>I have a cheap little radio that runs on AC or batteries, a Jensen
MR-550, fwiw. The voltage coming out of the power transformer is zero.
Between the prongs on the AC plug it has 580 ohms. It also says it has
a "thermal fuse fitted D 125 0" (I think the last digit is a zero.) But
I haven't foudn the fuse yet. Would the fuse be in the secondary
circuit? I thought it would be in the primary but there is ocntinuity
there, 580 ohms. My friend says it wroked fine for the first 2 months
and then went dead.
I'm making progress.
>You can measure the impedance of the transformer output,>
It is infinite.
>but thermal>
fuses are normally placed in the primary.
That's what I thought.
>Check for dry solder joints on the transformer pins.>
No pins. Primary wires connected to line cord and covered with
heatshink tubing. 580 ohma between them.
Secondary wire straight to little circuit board, which has diodes on it.
I took out the transformer and I don't see where the fuse would be.
Maybe next to the windings.
>
It also runs on 4 C-batteries. My friend says that doesn't work either,
And when I tried it with a universal charger, set to 6v, it didn't work,
nor with the polarity reversed. Not a peep out of it on AM or FM across
the whole dial.
>
Oops. should I have tried 7.5 and 9 volts too?
>but things don't usually break in two ways at once, especially a Jensen
radio, even if cheap. Maybe one of his batteries was dead. If the 4
batteries put out 6v DC, what should the AC output voltage of the
transformer be to get 6 volts for the radio?
>
Or I could assume it's the fuse, take the current one apart, find the
fuse, bypass it, on the theory that the fuse should have been in the
primary anyhow. ??????
>
Getting it to work with batteries would be step one.
Check the on/off switch. Trace battery voltages.
RL
| Date | Sujet | # | Auteur | |
| 12 Mar 26 |  Re: LIttle cheap readido is dead. Thermal fuse? | 3 | legg | |
| 14 Mar 26 |   Re: LIttle cheap readido is dead. Thermal fuse? | 1 | legg | |
| 14 Mar 26 |  Re: LIttle cheap readido is dead. Thermal fuse? | 1 | legg |
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