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Groups > sci.electronics.repair > #101795 > unrolled thread

LIttle cheap readido is dead. Thermal fuse?

Started bymicky <NONONOmisc07@fmguy.com>
First post2026-03-12 01:00 -0400
Last post2026-04-12 23:38 -0400
Articles 10 — 4 participants

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  LIttle cheap readido is dead.  Thermal fuse? micky <NONONOmisc07@fmguy.com> - 2026-03-12 01:00 -0400
    Re: LIttle cheap readido is dead.  Thermal fuse? legg <legg@nospam.magma.ca> - 2026-03-12 09:24 -0400
      Re: LIttle cheap readido is dead.  Thermal fuse? micky <NONONOmisc07@fmguy.com> - 2026-03-13 22:44 -0400
        Re: LIttle cheap readido is dead.  Thermal fuse? micky <NONONOmisc07@fmguy.com> - 2026-03-13 23:10 -0400
          Re: LIttle cheap readido is dead.  Thermal fuse? legg <legg@nospam.magma.ca> - 2026-03-14 08:59 -0400
          Re: LIttle cheap readido is dead.  Thermal fuse? legg <legg@nospam.magma.ca> - 2026-03-14 10:03 -0400
    LIttle cheap readido is dead. Thermal fuse? NOSPAM.Ed.Vance@darkrealms.ca (Ed Vance) - 2026-03-22 20:11 +0000
      Re: LIttle cheap readido is dead. Thermal fuse? Chuck <chuck23@dejanews.net> - 2026-03-23 09:49 -0500
        Re: LIttle cheap readido is dead. Thermal fuse? NOSPAM.Ed.Vance@darkrealms.ca (Ed Vance) - 2026-03-24 20:31 +0000
        Re: LIttle cheap readido is dead. Thermal fuse? micky <NONONOmisc07@fmguy.com> - 2026-04-12 23:38 -0400

#101795 — LIttle cheap readido is dead. Thermal fuse?

Frommicky <NONONOmisc07@fmguy.com>
Date2026-03-12 01:00 -0400
SubjectLIttle cheap readido is dead. Thermal fuse?
Message-ID<9lg4rk95mtvr3g4a75md7rnol063ucdnqa@4ax.com>
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. 

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#101797

Fromlegg <legg@nospam.magma.ca>
Date2026-03-12 09:24 -0400
Message-ID<khf5rkh5okla22epajq83f11skr1v96okb@4ax.com>
In reply to#101795
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. 

You can measure the impedance of the transformer output, but thermal 
fuses are normally placed in the primary.

Check for dry solder joints on the transformer pins.

RL

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#101805

Frommicky <NONONOmisc07@fmguy.com>
Date2026-03-13 22:44 -0400
Message-ID<b4i9rk9sn2egrlrbjrfen60flfdg6i6l3r@4ax.com>
In reply to#101797
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,
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. ??????

>RL

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#101806

Frommicky <NONONOmisc07@fmguy.com>
Date2026-03-13 23:10 -0400
Message-ID<o7k9rkpupsqkdbvfi3jlij2f2ifqpt7ofb@4ax.com>
In reply to#101805
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. ??????
>
>>RL

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#101807

Fromlegg <legg@nospam.magma.ca>
Date2026-03-14 08:59 -0400
Message-ID<somark5upinp7io20sn7ec27rctc3cm6pe@4ax.com>
In reply to#101806
On Fri, 13 Mar 2026 23:10:07 -0400, micky <NONONOmisc07@fmguy.com>
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

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#101808

Fromlegg <legg@nospam.magma.ca>
Date2026-03-14 10:03 -0400
Message-ID<ldqarkhb82idcmakqvi3rdike40beaao0q@4ax.com>
In reply to#101806
On Fri, 13 Mar 2026 23:10:07 -0400, micky <NONONOmisc07@fmguy.com>
wrote:


check also the battery/mains switch, or whatever is present to 
switch between the two,if only an orring diode.

Check speaker contacts . . .you won't get any noise out 
of it (turn-on click or background static) if it's 
disconnected.

RL 

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#101818 — LIttle cheap readido is dead. Thermal fuse?

FromNOSPAM.Ed.Vance@darkrealms.ca (Ed Vance)
Date2026-03-22 20:11 +0000
SubjectLIttle cheap readido is dead. Thermal fuse?
Message-ID<774228534@darkrealms.ca>
In reply to#101795
> From: NONONOmisc07@fmguy.com

> 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.

> --- SoupGate-Win32 v1.05
>  * Origin: you cannot sedate... all the things you hate (1:229/2)


Mickey, In the late 1950's I got my first AlliedRadio catalog.
I also hung around the Hi-Fi section of a store.

My thoughts back then was Jensen was one of the better brands as Bogen 
(Bogan?)
was 

Myself, I didn't buy the high priced spread.
My Stereo amplifier was a Heathkit AA-32. <G R I N>
Ed

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#101819 — Re: LIttle cheap readido is dead. Thermal fuse?

FromChuck <chuck23@dejanews.net>
Date2026-03-23 09:49 -0500
SubjectRe: LIttle cheap readido is dead. Thermal fuse?
Message-ID<pFLBaVZrKD9IzanI=Iw0bmAWvHHH@4ax.com>
In reply to#101818
On Sun, 22 Mar 2026 20:11:57, NOSPAM.Ed.Vance@darkrealms.ca (Ed Vance)
wrote:

>
>> From: NONONOmisc07@fmguy.com
>
>> 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.
>
>> --- SoupGate-Win32 v1.05
>>  * Origin: you cannot sedate... all the things you hate (1:229/2)
>
>
>Mickey, In the late 1950's I got my first AlliedRadio catalog.
>I also hung around the Hi-Fi section of a store.
>
>My thoughts back then was Jensen was one of the better brands as Bogen 
>(Bogan?)
>was 
>
>Myself, I didn't buy the high priced spread.
>My Stereo amplifier was a Heathkit AA-32. <G R I N>
>Ed
The thermal fuse is usually under the transformer windings wrap.

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#101820 — Re: LIttle cheap readido is dead. Thermal fuse?

FromNOSPAM.Ed.Vance@darkrealms.ca (Ed Vance)
Date2026-03-24 20:31 +0000
SubjectRe: LIttle cheap readido is dead. Thermal fuse?
Message-ID<774402527@darkrealms.ca>
In reply to#101819
> From: chuck23@dejanews.net

> On Sun, 22 Mar 2026 20:11:57, NOSPAM.Ed.Vance@darkrealms.ca (Ed 
> Vance)
> wrote:

> The thermal fuse is usually under the transformer windings wrap.

> --- SoupGate-Win32 v1.05
>  * Origin: you cannot sedate... all the things you hate (1:229/2)


Chuck, My post to Micky was only a comment in this thread.
I am sure Micky read your post about the thermal fuse and appreciated 
the help.
Ed

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#101831 — Re: LIttle cheap readido is dead. Thermal fuse?

Frommicky <NONONOmisc07@fmguy.com>
Date2026-04-12 23:38 -0400
SubjectRe: LIttle cheap readido is dead. Thermal fuse?
Message-ID<o6potk50okeh5cjimffc55iie7419v4bt1@4ax.com>
In reply to#101819
In sci.electronics.repair, on Mon, 23 Mar 2026 09:49:08 -0500, Chuck
<chuck23@dejanews.net> wrote:

>On Sun, 22 Mar 2026 20:11:57, NOSPAM.Ed.Vance@darkrealms.ca (Ed Vance)
>wrote:
>
>>
>>> From: NONONOmisc07@fmguy.com
>>
>>> 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.
>>
>>> --- SoupGate-Win32 v1.05
>>>  * Origin: you cannot sedate... all the things you hate (1:229/2)
>>
>>
>>Mickey, In the late 1950's I got my first AlliedRadio catalog.
>>I also hung around the Hi-Fi section of a store.
>>
>>My thoughts back then was Jensen was one of the better brands as Bogen 
>>(Bogan?)
>>was 
>>
>>Myself, I didn't buy the high priced spread.
>>My Stereo amplifier was a Heathkit AA-32. <G R I N>
>>Ed
>The thermal fuse is usually under the transformer windings wrap.

Aha, maybe it is in the secondary for some reason.  I'm out of town but
I'll look when I get home.    I need to ask if he uses mostly batteries
or AC for the radio. 


BTW, they have the very radio on ebay for iirc $25, so I shouldn't spend
forever on this. 

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