Schematic for RCA RS2640

[Jazz P Bass]

Pin #9 is the Standby pin.

If it never raises above the zero volts that you measured, then the power amp ic is in standby.

[shortcircuit]

Pin #9 is the Standby pin.

If it never raises above the zero volts that you measured, then the power amp ic is in standby.

[ATTACH=CONFIG]47921[/ATTACH]

I get .064vdc on pin9 , with fm radio which is not 0vdc thank you, when this was working the fan only came on once you increased the volume , should this be running constantly?? It does run with direct 9v to it. I'm going to back track

[Jazz P Bass]

Follow pin 9 (Standby) and pin 10 (Mute) on the schematic.

Q501 (NPN transistor) is the active control element.

rca_rs2640 Mute.pdf

[shortcircuit]

Follow pin 9 (Standby) and pin 10 (Mute) on the schematic.

Q50 9 (NPN transistor) is the active control element.

[ATTACH]47925[/ATTACH]

I think you meant Q501 ,this flea
testing in circuit DVM on diode mode, Blk to Base Red to Emitter .970 red to Collector 1.322 Red to base Blk to Emitter .699 Blk to collector .696

[g1]

How about D504 and D501?
What kind of voltages do you get at E,B,&C of Q501 ?

[shortcircuit]

How about D504 and D501?
What kind of voltages do you get at E,B,&C of Q501 ?

D504 cathode 11.75vdc anode 9.34vdc D501 cathode 5.22vdc anode 0vdc , Q501 E =0vdc B= .140vdc C= 5.22vdc

in diode mode in circuit
D504 + to C / - to A 1.163 - to C / + to A .700
D501 + to C / - to A .683 - to C / + to A .654

[Jazz P Bass]

"Q501 E =0vdc B= .140vdc C= 5.22vdc"

So, if Q501 Collector is sitting at 5.22Vdc, why are the standby & mute pins (Pin 9 &10) at 0 volts?

[shortcircuit]

"Q501 E =0vdc B= .140vdc C= 5.22vdc"

So, if Q501 Collector is sitting at 5.22Vdc, why are the standby & mute pins (Pin 9 &10) at 0 volts?

Q501 is a problem child and not turning on

[Jazz P Bass]

Q501 is a problem child and not turning on

Yeah but....

Q501, if on, would pull the collector low and it is not low.
It's at 5Vdc.

So the question remains: 'why are pin 9 & 10 low?'

[shortcircuit]

Yeah but....

Q501, if on, would pull the collector low and it is not low.
It's at 5Vdc.

So the question remains: 'why are pin 9 & 10 low?'

this is humbling , had headphones plugged in . Now on IC 501 I have 5.20vdc on pin 9 and 5.15vdc on pin 10 , buzz, no audio

[J M Fahey]

So the question remains: 'why are pin 9 & 10 low?'

Thank you JPB.

If you donŽt mind, IŽll use that as the title of my next Movie.
Regards
Alfred.

[shortcircuit]

this is humbling , had headphones plugged in . Now on IC 501 I have 5.20vdc on pin 9 and 5.15vdc on pin 10 , buzz, no audio

Jazz P Bass(or any supporting member) are you still seeing something obvious that I'm missing completely ?? besides my incompetence, if yes keep asking ?? don't just give the answer. Going back this actually quit while it was in standby mode , just plugged in with the clock,should I be focusing on IC401? no signal to amplify ?. This unit isn't worth a free lunch to start with , thought it would be a good solid state learning tool, and it has been with the patience of the supporting members here .

[g1]

I think you are correct, look at IC401.
If you are hearing hum and the volume control seems to make an audible change, the power amp is probably ok. I assume you listened to the phones and didn't hear anything there either?
And you said the fault was originally intermittent, have you tapped around with a chopstick to see if there is a physical connection issue?
There are some DC voltages listed for IC401 on page 20 of the service manual. Also check for any audio at the L & R output pins. If you do have audio there, then you can return to the power amp.

[shortcircuit]

I think you are correct, look at IC401.
If you are hearing hum and the volume control seems to make an audible change, the power amp is probably ok. I assume you listened to the phones and didn't hear anything there either?
And you said the fault was originally intermittent, have you tapped around with a chopstick to see if there is a physical connection issue?
There are some DC voltages listed for IC401 on page 20 of the service manual. Also check for any audio at the L & R output pins. If you do have audio there, then you can return to the power amp.

Hear a hum ,and low audio clicks when volume is increased ,no audio increase , correct nothing from headphones. Here is the only ic401 voltage chart I have , and my readings
I don't trust the chart, voltage chart for ic501 wasn't even close. Wouldn't it be odd that both audio IC's go out ?. Thanks for the reply

[g1]

Well, hopefully it's the correct schematic, otherwise we're probably beat.
Look at the audio switching IC page (pg.13 of pdf), there should be 6.8VDC coming in on pin 4 of P301 connector. Do you have that? You have nothing on pin 24 of IC401, which is supposed to be the supply pin. The unit is not in stand-by mode is it? Does the part number on IC401 match what the schematic shows, TDA7440 ?