I recently pick up a Radio Shack wireless mic at Goodwill for $1. I
could hear something in the receiver ratting, so I figured it wouldn't work. I was right. It turns out that the receiver has two crystals: 10.245 Mhz and 39.190 Mhz. The 39.190 Mhz crystal was cleanly broken
away from the PCB and making the rattling when moved. Problem is that
the break was so close to the case that there's nothing left to solder
to, so I need a new crystal. I see one on the "bay" but about $10 by
the time shipping and tax are added, which sort of defeats the purpose
of a bargain. So, what about this crystal instead?
https://www.digikey.com/en/products/detail/abracon-llc/ABLS-13-0625MHZ-10-K4Q-T/2184092
Most likely the native crystal was working from a fundamental overtone anyway. The frequency of the above one gets me close to the frequency needed, but not quite. Assuming this crystal would even work, would a series trimmer cap allow me to adjust to the proper frequency?
Thank you.
On 1/23/22 19:52, bilou wrote:
Le 23/01/2022 à 18:01, -faver- a écrit :
I recently pick up a Radio Shack wireless mic at Goodwill for $1. I
could hear something in the receiver ratting, so I figured it wouldn't
work. I was right. It turns out that the receiver has two crystals:
10.245 Mhz and 39.190 Mhz. The 39.190 Mhz crystal was cleanly broken
away from the PCB and making the rattling when moved. Problem is that
the break was so close to the case that there's nothing left to solder
to, so I need a new crystal. I see one on the "bay" but about $10 by
the time shipping and tax are added, which sort of defeats the purpose
of a bargain. So, what about this crystal instead?
https://www.digikey.com/en/products/detail/abracon-llc/ABLS-13-0625MHZ-10-K4Q-T/2184092
Most likely the native crystal was working from a fundamental overtone
anyway. The frequency of the above one gets me close to the frequency
needed, but not quite. Assuming this crystal would even work, would a
series trimmer cap allow me to adjust to the proper frequency?
Thank you.
Worth a try IMHO.
Think also on the possibility of slightly modifying the 10.245 or the transmitter oscillator.
Wish there was a schematic somewhere for these. The units themselves
are all over the net for sale. Doesn't look like they are the best performers.
** So the mic is on 49 MHz - right ?
The crystal is an SMD type that just * fell* off the PCB ???
Please explain.
Yes, 49 Mhz system. The crystal housing is HC-49/U. No, it didn't
fall, it looks to me like the leads corroded away right at the PCB. The
old yellowed glue is left behind with the imprint of where the crystal
was. I've read how corrosive some of these glues could be and I think
that's what destroyed the crystal leads.
** Absolutely !
Seen the exact thing, many times - in powered loudspeakers made by dB Technologies.
Damn "yellow peril" glue !
4MHz crystals in the DSP system * corroded * right off the PCB and the whole thing stops.
Do you have a matching receiver for 49.xxx MHz ?
IMO you repair idea sounds unlikely to work out - crystal oscillators are fussy and those models are narrow band, about 25kHz IIRC.
Mics on higher bands like 175MHz are often 250KHz wide.
FM wireless mics are non simple, but fun to fix.
.... Phil
Do you have a matching receiver for 49.xxx MHz ?
IMO you repair idea sounds unlikely to work out - crystal oscillators are fussy and those models are narrow band, about 25kHz IIRC.
Mics on higher bands like 175MHz are often 250KHz wide.
FM wireless mics are non simple, but fun to fix.
Well, I do have a radio scanner.
That's how I knew that the transmitter
at least was working. It seems to be on frequency although, consistent
with the reputation I read about these units, the audio frequency range leaves a lot to be desired.
I absolutely hate that glue!
So you don't think using the overtone of the crystal I mentioned will
serve as a working substitute for the broken off one?
I recently pick up a Radio Shack wireless mic at Goodwill for $1. I
could hear something in the receiver ratting, so I figured it wouldn't work. I was right. It turns out that the receiver has two crystals: 10.245 Mhz and 39.190 Mhz. The 39.190 Mhz crystal was cleanly broken
away from the PCB and making the rattling when moved. Problem is that
the break was so close to the case that there's nothing left to solder
to, so I need a new crystal. I see one on the "bay" but about $10 by
the time shipping and tax are added, which sort of defeats the purpose
of a bargain. So, what about this crystal instead?
https://www.digikey.com/en/products/detail/abracon-llc/ABLS-13-0625MHZ-10-K4Q-T/2184092
Most likely the native crystal was working from a fundamental overtone anyway. The frequency of the above one gets me close to the frequency needed, but not quite. Assuming this crystal would even work, would a series trimmer cap allow me to adjust to the proper frequency?
Thank you.
I recently pick up a Radio Shack wireless mic at Goodwill for $1. I
could hear something in the receiver ratting, so I figured it wouldn't work. I was right. It turns out that the receiver has two crystals: 10.245 Mhz and 39.190 Mhz. The 39.190 Mhz crystal was cleanly broken
away from the PCB and making the rattling when moved. Problem is that
the break was so close to the case that there's nothing left to solder
to, so I need a new crystal. I see one on the "bay" but about $10 by
the time shipping and tax are added, which sort of defeats the purpose
of a bargain. So, what about this crystal instead?
https://www.digikey.com/en/products/detail/abracon-llc/ABLS-13-0625MHZ-10-K4Q-T/2184092
Most likely the native crystal was working from a fundamental overtone anyway. The frequency of the above one gets me close to the frequency needed, but not quite. Assuming this crystal would even work, would a series trimmer cap allow me to adjust to the proper frequency?
Thank you.
On 24/01/2022 04:01, -faver- wrote:
I recently pick up a Radio Shack wireless mic at Goodwill for $1. I
could hear something in the receiver ratting, so I figured it wouldn't
work. I was right. It turns out that the receiver has two crystals:
10.245 Mhz and 39.190 Mhz. The 39.190 Mhz crystal was cleanly broken
away from the PCB and making the rattling when moved. Problem is that
the break was so close to the case that there's nothing left to solder
to, so I need a new crystal. I see one on the "bay" but about $10 by
the time shipping and tax are added, which sort of defeats the purpose
of a bargain. So, what about this crystal instead?
https://www.digikey.com/en/products/detail/abracon-llc/ABLS-13-0625MHZ-10-K4Q-T/2184092
Most likely the native crystal was working from a fundamental overtone
anyway. The frequency of the above one gets me close to the frequency
needed, but not quite. Assuming this crystal would even work, would a
series trimmer cap allow me to adjust to the proper frequency?
Thank you.
Bearing in mind that the thing cost you $1, you could try scraping away
at the glass around what is left of the crystal pin, to expose as much
metal as you can on the wire, and then joining on a fine strand of wire
with silver conductive paint (for example the type used to repair car
window de-misters). Once you have a good electrical connection, you can
cover the joint with 2-part epoxy (araldite etc.) to make it robust.
It is also possible to remove crystals from their metal can, it may
still work if you are careful and there will be much more wire to make contact to inside the can.
If you think the thing is worth much more than $1, you can either order
a custom crystal or use a PLL frequency sythesiser chip like the ones
from Silabs that radio amateurs often use as a local oscillator - they
are very simple to use and can produce whatever frequency you need. The frequency can be programmed with some arduino-type processor etc.
On 1/26/2022 2:37 AM, Chris Jones wrote:
On 24/01/2022 04:01, -faver- wrote:
I recently pick up a Radio Shack wireless mic at Goodwill for $1. I
could hear something in the receiver ratting, so I figured it
wouldn't work. I was right. It turns out that the receiver has two
crystals: 10.245 Mhz and 39.190 Mhz. The 39.190 Mhz crystal was
cleanly broken away from the PCB and making the rattling when moved.
Problem is that the break was so close to the case that there's
nothing left to solder to, so I need a new crystal. I see one on the
"bay" but about $10 by the time shipping and tax are added, which
sort of defeats the purpose of a bargain. So, what about this
crystal instead?
https://www.digikey.com/en/products/detail/abracon-llc/ABLS-13-0625MHZ-10-K4Q-T/2184092
Most likely the native crystal was working from a fundamental
overtone anyway. The frequency of the above one gets me close to the
frequency needed, but not quite. Assuming this crystal would even
work, would a series trimmer cap allow me to adjust to the proper
frequency?
Thank you.
Bearing in mind that the thing cost you $1, you could try scraping
away at the glass around what is left of the crystal pin, to expose as
much metal as you can on the wire, and then joining on a fine strand
of wire with silver conductive paint (for example the type used to
repair car window de-misters). Once you have a good electrical
connection, you can cover the joint with 2-part epoxy (araldite etc.)
to make it robust.
It is also possible to remove crystals from their metal can, it may
still work if you are careful and there will be much more wire to make
contact to inside the can.
If you think the thing is worth much more than $1, you can either
order a custom crystal or use a PLL frequency sythesiser chip like the
ones from Silabs that radio amateurs often use as a local oscillator -
they are very simple to use and can produce whatever frequency you
need. The frequency can be programmed with some arduino-type processor
etc.
I was thinking the same thing. When I was a tech we used silver, and
gold conductive epoxy to attach surface mount components. Once cured it
was quite strong.
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