Hi all,
So I scoped the rails of this Uher tap deck I've been working on and
they were noisy as hell; a lot of ugly ripple coming from the wall
wart supply it runs off. So before I can establish what if anything is
amiss with the deck, I need to stabilize it's power source and get rid
of all the crap. This will probably mean junking the wall wart; no
biggie in the grand overall scheme of things. Anyway, there was a
bulge about half way down the power lead which someone had covered in >shrink-wrap. I assumed this would be bullet connectors, but on tearing
it down, it transpired the same someone had fitted a 1 ohm 6W resistor
into the pos lead. Looks like it's all been done professionally, but >certainly not from the factory. Why would anyone fit a 1 ohm resistor
in the power lead? I assume there must be a good reason for it, but
whatever it is, I can't figure it out. Any ideas?
Your pal,
CD.
On Sun, 12 Apr 2026 17:51:30 +0100, Cursitor Doom <cd@notformail.com>
wrote:
Hi all,
So I scoped the rails of this Uher tap deck I've been working on and
they were noisy as hell; a lot of ugly ripple coming from the wall
wart supply it runs off. So before I can establish what if anything is >amiss with the deck, I need to stabilize it's power source and get rid
of all the crap. This will probably mean junking the wall wart; no
biggie in the grand overall scheme of things. Anyway, there was a
bulge about half way down the power lead which someone had covered in >shrink-wrap. I assumed this would be bullet connectors, but on tearing
it down, it transpired the same someone had fitted a 1 ohm 6W resistor
into the pos lead. Looks like it's all been done professionally, but >certainly not from the factory. Why would anyone fit a 1 ohm resistor
in the power lead? I assume there must be a good reason for it, but >whatever it is, I can't figure it out. Any ideas?
Your pal,
CD.
Some possible reasons for the 1 ohm resistor:
1. Easy way to measure the current using a voltmeter.
2. Substitute for a fuse. If too much current, the resistor
explodes.
3. Part of an RC ripple filter.
4. Limit inrush surge current.
5. Crude slow blow fuse. High current spike will not produce enough
current to blow the cheap fast blow fuse.
My best guess(tm) is #1.
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Sun, 12 Apr 2026 17:51:30 +0100, Cursitor Doom <cd@notformail.com>
wrote:
Hi all,
So I scoped the rails of this Uher tap deck I've been working on and
they were noisy as hell; a lot of ugly ripple coming from the wall
wart supply it runs off. So before I can establish what if anything is
amiss with the deck, I need to stabilize it's power source and get rid
of all the crap. This will probably mean junking the wall wart; no
biggie in the grand overall scheme of things. Anyway, there was a
bulge about half way down the power lead which someone had covered in
shrink-wrap. I assumed this would be bullet connectors, but on tearing
it down, it transpired the same someone had fitted a 1 ohm 6W resistor
into the pos lead. Looks like it's all been done professionally, but
certainly not from the factory. Why would anyone fit a 1 ohm resistor
in the power lead? I assume there must be a good reason for it, but
whatever it is, I can't figure it out. Any ideas?
Your pal,
CD.
Some possible reasons for the 1 ohm resistor:
1. Easy way to measure the current using a voltmeter.
2. Substitute for a fuse. If too much current, the resistor
explodes.
3. Part of an RC ripple filter.
4. Limit inrush surge current.
5. Crude slow blow fuse. High current spike will not produce enough
current to blow the cheap fast blow fuse.
My best guess(tm) is #1.
Mistaken belief that it would prevent the supply voltage rising to
too-high a value?
On Mon, 13 Apr 2026 08:58:14 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Sun, 12 Apr 2026 17:51:30 +0100, Cursitor Doom <cd@notformail.com>
wrote:
Hi all,
So I scoped the rails of this Uher tap deck I've been working on and
they were noisy as hell; a lot of ugly ripple coming from the wall
wart supply it runs off. So before I can establish what if anything is
amiss with the deck, I need to stabilize it's power source and get rid
of all the crap. This will probably mean junking the wall wart; no
biggie in the grand overall scheme of things. Anyway, there was a
bulge about half way down the power lead which someone had covered in
shrink-wrap. I assumed this would be bullet connectors, but on tearing
it down, it transpired the same someone had fitted a 1 ohm 6W resistor
into the pos lead. Looks like it's all been done professionally, but
certainly not from the factory. Why would anyone fit a 1 ohm resistor
in the power lead? I assume there must be a good reason for it, but
whatever it is, I can't figure it out. Any ideas?
Your pal,
CD.
Some possible reasons for the 1 ohm resistor:
1. Easy way to measure the current using a voltmeter.
2. Substitute for a fuse. If too much current, the resistor
explodes.
3. Part of an RC ripple filter.
4. Limit inrush surge current.
5. Crude slow blow fuse. High current spike will not produce enough
current to blow the cheap fast blow fuse.
My best guess(tm) is #1.
Mistaken belief that it would prevent the supply voltage rising to
too-high a value?
When Mr Doom posted his initial saga of his attempt to repair his tape
deck, I had to ask that he supply the model number so that anyone
could provide usable repair solutions. A sure sign of model number
paranoia. My crystal ball indicated that we would be cursed with
multiple repetitions, so I downloaded a schematic and saved it. Upon >inspection, it's an Uher 4000 tape deck which operates from a 6 to
7.5v internal battery. It also has an external power connector. The >schematic shows that after the on/off switching maze, there sits a
7.3-7.7v zener diode across the power line. Oddly, I don't see a fuse
on the schematic.
The zener "crowbar" should be sufficient to protect the circuitry from
low energy over voltage spikes. There's no protection against
plugging the battery in backwards or connecting a power source with
too high a voltage. Note that the battery power is positive ground,
which might inspire a reverse polarity accident from those (like me)
who are accustomed to negative ground systems. If the battery is
reversed, a 1 ohm resistor might keep the current low enough (6 watts)
to prevent starting a fire.
Free download or full manual including a readable schematic: ><https://elektrotanya.com/uher_4000_report-l_4200_4400_report_stereo_sm.pdf/download.html>
Be sure that cookies are enabled for this web side or it will refuse
to allow downloads.
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