don't worry it's just a hobby project
used 7.1 audio receiver almost anywhere these days for about $50 is that on flebay
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don't worry it's just a hobby project
used 7.1 audio receiver almost anywhere these days for about $50 is that on flebay
kijiji,ebay or pawnshops.Quote:
Originally Posted by skywalker999
It looks like there is an overload detection circuit, it uses a relay to cut off the power to the audio amps, look for RY501 and see if it is stuck on/off or being turned on/off permanently by Q523 or Q524 being turn on, blown or shorted.
Terryl is that on the front panel because i don't see it on the amp board
Look right next to the power supply transformer and close to one of the large caps.
Attachment 18801
Thanks Terryl founded how do you turn that on is there a switch on that or something else turns that on
That should be on when the stereo is on, it turns off when an overload is detected, if it has never been used then the circuit may have popped when your brother overloaded it.
The relay can only be tested when the stereo is on and connected, you can check for a DC voltage at R608, then on the other side of the relays coil there should be a low voltage, say around .6 volts or so, this can be measured at the second jumper over at the top of cap C607, you can see the trace in the photo I posted.
This relay will be on when one side is at (lets say) 12 volts, and the other side is at 0 volts, if both sides are at 12 volts or 0 volts then the relay will not turn on.
Now I am assuming that the relay is always on when the stereo is on, so one side will be a high voltage, the other a low, if both sides are the same then the circuit is ether on because it still detects an overload, or the circuit is popped.
Or the relay coil has gone bad, you can measure across it with an ohm meter, in circuit there should be some resistance across the coil, if you read an open then the relay is gone.
The coil resistance may be marked on the relay.
those transistors look good they are hi power and will give readings like you got. re-install them. when you power up do you here a clicking noise. that would be the relay turning on. some times you can even feel it turn with your finger.
terry good call i was going to go there with the readings from the transistors.
for those resistors sky use the lowest reading on meter. 200 ohm
first of course re-install the transistors.
that relay if its bad is no longer available. pioneer no longer stocks it even the recommended # not available.
to test check for continuity where i put blue line. if good then pull relay and add jumpers that i marked in pic in red.
that will bypass the relay with jumpers (temp) and test receiver with speakers connected.
if that works your not out of the woods you will need to determine what went bad in the overload circuit.
if you have spare time and want to play some you could build this simple transistor tester (circuit posted) which will greatly improve and reduce testing time as you can test while in circuit. as you see parts count is small use bread board to mount and use mini grabbers for leads.
or you can get a kit from h**p://www.tequipment.net/ElencoDT-100K.html?Source=Google&gclid=CKOYnuOQkbgCFdB7Qgod vDoAog
i have the same one works great. just change the clips to mini grabbers. they sell it for 20 bucks. should not take more than an hr or 2 to assemble.
Terryl and nunoit i get 48.2V on that resistor R608 but I'm getting no voltage on that coil
and other places close to that coil the other coil im getting 45.3V check pic
and connected two 8 ohm speakers on the amp to test but there is no clicking sound coming from
RY501
Attachment 18834
Use a real long screw driver, touch it to the relay then hold your ear to the handle of the screw driver, turn the power on and off, if you don't hear anything then the circuit driving the relay is dead, or the relay is gone.
first check continuity across the coil of the relay. should read dead short if good, if not remove and find out voltage and replace.
yours is DPST (double pole single through) take to store to match pin out.
note: most relays come with 8 pins not 6 like yours. (normally open, common to both, normally closed and the coil) you need normally open contacts. once you find one, you may and will have to cut 2 pins (normally closed) flush to body to mount it.
if good then track down and test Q-601, Q-602, Q-604, then also look for Q-523 and Q-524, diodes are D-507 D-508, D-509, D-510 and zener D-610 also caps c-603, c-604, c-605, c-523, and c-524 those are all part of the overload circuit.
note: the zener diode is a voltage regulator the component # will aid you what voltage it regulates to. you need to look up specks for that info. that should tell you the coil voltage to.
my suspicion is the one mounted on the heat sink is bad, just my thought.
all those parts should be where marked on red on pic.
BTW: your doing great you will be done soon.
OK, for that circuit the transistors Q523 and 524 are the overload detectors, they look for too much current or DC voltage across the power amp transistors Q1, 2, 3 and 4, if they detect to high a DC voltage or current they will turn on and cause Q601 and Q602 to do there thing and turn Q604 off, thus shutting off the relay RY501, as the DC voltage across the coil will be the same and that shuts off the sound to the speakers.
I would check with a small speaker at L501 and L502 (carefully, with the volume down low) (I would use an oscilloscope for this, but you might not have one of those)to see if you have any sound at that point, if you do then we are looking at the right circuit as it is keeping RY501 from closing and delivering the sound to the rear speaker terminals.
Thanks guys but that's a lot of home work for one day lol
thanks for the link nunoit but unfortunately don't think they ship north of the boarder (canada ) ad to by same exact one on ebay
40 dollars shipping included and I'm still waiting for my new cap tester to bad I couldn't get one capable of testing over 2000uf
will get back as soon as possible
NEC 78M12
8752J
I removed this part to test and fund that the heat sink was not soldered to the board
Here are the results
Red on pin 1 black on pin 3 = OL
Black on pin 1 red on pin 3 =.577
Red on pin 1 black on pin 2 = OL
Black on pin 1 red on pin 2 = .576
Black on pin 2 red on pin 3 =1.973
Red on pin 2 black on pin 3 = .634
So is this correct
I also removed RY501 will check at my local electronic parts store and see if they have that part or something similar
Terryl did that screwdriver test nothing no clicking noise
And nunoit there is five or six zener diodes on that spot are those tested just like a regular diode
the 78m12 is a 12v regulator readings should be good. remount and check for 12v on pin 3. mounted and looking at front pins are left to right 1 input 2 ground 3 12 v output. test while mounted and powered up.
also my bad since its a 12 v regulator it has nothing to do with the over load circuit.
on the relay there are 6 pins 4 close together 2 on other end, the 2 by them self's are the coil. set you meter for ohms any one will do touch leads together. should read shorted.(continunity) now touch the 2 pins on the relay, you should read shorted. if not relay is bad. you can test the other 4 as well they should read open any combination of the 4 pins.
picture and schematics show the other zener diodes are for the power supply. according to the schematic the only zener diode for the relay is D-610, and is also 12 v regulator. from the side with the band you should get 12 v while powered up. as long as Q-601, Q-602, Q-604 and Q-605 (power off mute) transistors are working.
which leads to a mute circuit which could also be a problem, if there is one that is. so test all the transistors that i said in previous post.
just some FYI
on analyzing the circuit when power is turned on Q's 605 and 604 apply power to relay, now Q's Q-523 and Q-524 monitor the right and left channels of the output amp, if all is good they send signal to Q-601, Q-602, which allows Q-604 to continue to function correctly. if not the relay turns off to protect the power transistors from burning up.
terryl i did not realize you had made the same analysis on the circuit. don't want step on toes. did not read your post.