Shure vintage wireless guitar, died ?

[ricci]

But if the quartz is broken, can it transmit something or does it no longer send anything? Yesterday i was listening in headphones and it happened that depending on where i touched the transmitter, occasionally i could hear something even if at a very low volume.

[Enzo]

If a crystal cracks, it generally becomes inert. In all my years, I have seen good ones, and ones that do not work. I don't recall ever seeing one that worked wrong.

[ricci]

Can i hope to find the wiring diagrams on the web ?

[Enzo]

What does it cost to look?

And try CALLING Shure Brothers and asking if they can provide the documents.

[ricci]

I had already sent an email, if they don't respond, patience.

[Enzo]

emails are OK< but CALLING has you talking to real people there.

[ricci]

Wow i found online the two Service manuals of the T1G transmitter and the T4G receiver.
https://manualzz.com/doc/778374/shure-t1-service-manual
https://manualzz.com/doc/6315640/ser...rsity-receiver

[ricci]

I measured some voltage (anomalous), I will not make current measurements, it's almost all smd ... anyway compared to what the Service Manual says, on IC MC33179, there must be audio signal both on pin 1 and on pin 7, on pin 1 there is but No Audio on pin 7; on pins 5-6-7 the voltages should all be 4.5 Vdc, everything ok except on pin 6, I find 3.9 Vdc, and on transistor Q204, Vc = 8.88 Vdc (ok on mine), Vb = 0 , 45 Vdc (on my 1.01 Vdc) and Ve = 0.473 Vdc (on my 0.35 Vdc).

On the receiver there are few voltage checks and I limited myself to following the Bench Checks of which only the DC Power is ok. As for the Audio section, I only managed to understand that in pin 6 of U1 and U2 there is no audio, or rather the transmitter signal does not arrive but I only hear a kind of white noise.

[ricci]

Sorry, i wrote about pin 1 of MC33179 of the transmitter but pin 1 i saw that it is not used, only pin 7 is tested but the audio is distorted like when a low battery and decays quickly without sustain. Although i can also hear the audio on pin 1 of the first opamp even if the first opamp is not used.

Regarding the NE571D chip of the transmitter, the audio on pin 7 is loud and clear while on pin 15 it is like pin 15 but without low frequencies.

[The Dude]

FWIW: If your diversity lights aren't lighting on the receiver, you are looking for an RF problem- not an audio problem.

[ricci]

The audio I found is present almost to the end, for example in TP3 to the left of this image,

https://ibb.co/q0WQ8gQ

shortly after there is the RF transistor Q204 with the wrong values and, immediately after, the antenna.
Do you think this could be the reason why the transmitter is not doing what it is supposed to, which is to transmit?

With the oscilloscope probe I touched one side of the quartz and an amplitude modulation appears. Can we say that quartz works right?
Thanks friend

[ricci]

The values that Q204 should have
Vc = 8.88 Vdc (8.89)
Vb = 0.45 Vdc (1.01)
Ve = 0.473 Vdc (0.35)

in brackets the values I read

[Helmholtz]

The values that Q204 should have
Vc = 8.88 Vdc (8.89)
Vb = 0.45 Vdc (1.01)
Ve = 0.473 Vdc (0.35)

in brackets the values I read

The Q204 voltages from the manual don't seem to make sense.
With Ve higher than Vb the transistor would be biased off, so no emitter current.
OTOH, 0.47V drop across the 33R emitter resistor means a current of 14mA.

The base voltage is derived from the 5V rail by the 6.8k and 2.2k.voltage divider resistors.
From this the base voltage should be around 1.2V.

I'd say your measured voltages make more sense than those from the manual.

[ricci]

I'd say your measured voltages make more sense than those from the manual.

So do you think the transmitter might not be the problem ?

[Helmholtz]

I'd say there's a chance that the transmitter is ok if you can see HF modulation at the collector of Q204.