Hi
Ive got this oldschool phoenix gold ZX450
when i plug it the OVL red light turns on for about 1 second then it turns off and the green power light lights up
but no audio is playing ...
I dont remember if it used to do this when powered up or if there was only the green light who lighted up.. so i dont know if its normal
Ive got this oldschool phoenix gold ZX450
when i plug it the OVL red light turns on for about 1 second then it turns off and the green power light lights up
but no audio is playing ...
I dont remember if it used to do this when powered up or if there was only the green light who lighted up.. so i dont know if its normal
Your light up sequence sounds fine. No signal out could be lots of things. I have seen the power supplies fail and blow all their internal fuse resistor protection and still give the proper light up sequence, but not supply any power inside.
Or it could be something simple like bad selector switches on the crossover board, or blown input ground resistors located behind the RCA's, or bad pots.
When the amp turns on, do you get all 8 of the red LEDs inside to light up ??? There should be 2 LEDs per channel X 4 channels = 8 red LEDs looking thru the left view port. If those are out you might have a bad power supply section. If they are on then its probably a front end crossover board problem....
Or it could be something simple like bad selector switches on the crossover board, or blown input ground resistors located behind the RCA's, or bad pots.
When the amp turns on, do you get all 8 of the red LEDs inside to light up ??? There should be 2 LEDs per channel X 4 channels = 8 red LEDs looking thru the left view port. If those are out you might have a bad power supply section. If they are on then its probably a front end crossover board problem....
I am sorry your version does not have the LEDs. I apologize as some Zx and all Ti amps had the LEDs, along with MS, MPS, MQ series amps. What version is you ZX ? they had two versions of many models.
A simple check of DC offset on the outputs will tell you if you have rail voltage or not. To measure this just turn the amp on like normal and place a DC voltmeter across each channels terminals. You should get something like 5 to 10 Milli-volts or 0.005 to 0.010 DC volts. This number can be higher depending on age and condition of the semiconductors in each channel, but will only be present if the power supply is functional.
If you get these small voltage reading I would tend to think your problems are back with the input board. RCA ground resistors, gain pots, selector switches for input and crossover configuration are typical issues on these.
Let me know what you find, and again I am sorry about the LED confusion
no problem mate
I dont know wich version i have how can i know ? the only thing written on it is the model and the amp is black
I will measure the outputs tomorrow and let you know (the amp is at my job)
since i dont have the diagrams i simply measured here and there on the FETs on leg 1 to see if i had 5v on the gates and i had 0V ... not 5v .. i measured a few of them since i didnt knew wich one were doing what exactly and they were all 0V
would you happen to have a diagram for that amp?
I dont know wich version i have how can i know ? the only thing written on it is the model and the amp is black
I will measure the outputs tomorrow and let you know (the amp is at my job)
since i dont have the diagrams i simply measured here and there on the FETs on leg 1 to see if i had 5v on the gates and i had 0V ... not 5v .. i measured a few of them since i didnt knew wich one were doing what exactly and they were all 0V
would you happen to have a diagram for that amp?
Black matte case should be version 2 , STP55N06 are your mosfets and they have 33 ohm fusible resistors on each fets gate lead. These can and do blow out if the supply fets die. What is your ground reference point testing these ?
0 volts on the gate leads might mean the amp has been inhibited from turning on by some fault yet unseen. The power supply is controlled by Thermal, and overload inputs along with DC rail failure detections. Any of these can turn the amp off.
Please test the DC output/offset and or read the DC on any of the main amp transistors ground referenced to toroid center tap and record any large DC voltages you get.
PG used a staggered dual supply where the Darlington output stages run at about ~+&- 42 volt DC, and the input stages run at~ +&-49 volts DC. So these are the big numbers you will see if the supply is functional.
It would not matter if I had the print for this amp, since I lack any permission to freely distribute any such information. Simply stated, I own what's in my mind from the last 20 years or so, but even some of that is questionable, and I don't want any issues from any intellectual property which I do not own. I hope you understand, and I will try my best to help you without upsetting the powers to be...
0 volts on the gate leads might mean the amp has been inhibited from turning on by some fault yet unseen. The power supply is controlled by Thermal, and overload inputs along with DC rail failure detections. Any of these can turn the amp off.
Please test the DC output/offset and or read the DC on any of the main amp transistors ground referenced to toroid center tap and record any large DC voltages you get.
PG used a staggered dual supply where the Darlington output stages run at about ~+&- 42 volt DC, and the input stages run at~ +&-49 volts DC. So these are the big numbers you will see if the supply is functional.
It would not matter if I had the print for this amp, since I lack any permission to freely distribute any such information. Simply stated, I own what's in my mind from the last 20 years or so, but even some of that is questionable, and I don't want any issues from any intellectual property which I do not own. I hope you understand, and I will try my best to help you without upsetting the powers to be...
the amp ground terminal is my reference
if it would be thermal or overload the leds would be lit ?
yeah i understand but its a pita for me to test some parts if i dont have a diagram and dont know where exactly the parts are located and where they lead...
I can try my best to get some readings but i would not even be shure i would measure the right spot..
when you say measure the DC output/offset do you mean both DCC probes at the speakers terminal ?
where are located the main amps transistors ? ( i will use the ground from the center tap of the toroid for those ones)
if it would be thermal or overload the leds would be lit ?
yeah i understand but its a pita for me to test some parts if i dont have a diagram and dont know where exactly the parts are located and where they lead...
I can try my best to get some readings but i would not even be shure i would measure the right spot..
when you say measure the DC output/offset do you mean both DCC probes at the speakers terminal ?
where are located the main amps transistors ? ( i will use the ground from the center tap of the toroid for those ones)
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There are component numbers and test points clearly marked on all the boards, and I have used them mostly for final alignment and some early on detection. If you have any questions regarding these test points just ask, and I will dig up my carcases and tech notes for you...
As I have said many times before, PG never publicly released any documents in their entire history. If they had I would have those public documents, and I would share them IF they had ever been public in the first place. I like repairing amps and helping other to do the same that is why I am here trying to be helpful. But getting into trouble over helping others is not part of my agenda....
As I have said many times before, PG never publicly released any documents in their entire history. If they had I would have those public documents, and I would share them IF they had ever been public in the first place. I like repairing amps and helping other to do the same that is why I am here trying to be helpful. But getting into trouble over helping others is not part of my agenda....
the exact model is ZX450B 00016 on the casing
on the speaker outputs i have voltage on all of them
i used the middle toroid connection on the left of the toroid cause there is nothing in the middle... 5 wire on the left 4 on the right and the middle on the left seems to be a ground... so i used that one...
i have
15mV left front speaker
25mV left rear speaker
8mV right front speaker
12mV right rear speaker
and there seems to be an error on the case for the polarity cause it ways +-+- and when i measure the positive for the right terminals are on the far right... like this +--+... dont know if its me .. anyways i have voltage on all of the 4 outer pins
for the transistors i will describing them with the power terminals to the right closest to me
the ones who are upright in free air...
there is the front row (closest to me) they all have 40V 3.25V 40V
the rear row (fartest to me) they all have 1.8V 41V 1.2V
I notice halfway that some reads negative and some reads positive voltages... i didnt take note at first so i will simply write the voltages ... hope this is not that important
after that the transistors under the heatsinks and fans..
the 8 big transistors are on my left...
they are a batch of normal transistors with TO-220FP casing aroung the bigger ones
they all read 1.7V 1.7V 1.0V and there are others wich are smaller and almost square with foam pads underneath them.. they all read 1.2V 35V 0.6V
then on the right there is a bunch of TO-220 transistors and 2 TO-220FP...
the 2 TO-220FP's legs looks weird... they are satinated not mettalic (like al the TO-220 on the right..) thats ok but they look kind of semi dark black (like when there is a short but no signs of shorts) anyways.. for those 2.. one reads 30V 0V 15V (the one the fartest of me) and the one closest to me reads 0V -25V -15V
then my partner noticed 2 of the big transistors Q118 and Q119 getting hot and what seems to be the transfo starting to wine a little we unplugged the amp and let it cool... now when we power the remote this sound is always present as soon as the amp gets the green light (after the 2second red OVL light) and the 2 big MJL3281A gets hot real quick... so we measured those 2 real fast and i reads
1-2 0 ohm
1-3 0.3ohm
2-3 0ohm
and the other
1-2 20k and lowering (capacitor)
1-3 120ohm
2-3 9.4Mohm
did we ****** something up removing the heatsinks and powered it for like not even a minute.. nothing seemed hot at first then all of a sudden thoese 2 gets hot and the transfo is winning a bit...
on the speaker outputs i have voltage on all of them
i used the middle toroid connection on the left of the toroid cause there is nothing in the middle... 5 wire on the left 4 on the right and the middle on the left seems to be a ground... so i used that one...
i have
15mV left front speaker
25mV left rear speaker
8mV right front speaker
12mV right rear speaker
and there seems to be an error on the case for the polarity cause it ways +-+- and when i measure the positive for the right terminals are on the far right... like this +--+... dont know if its me .. anyways i have voltage on all of the 4 outer pins
for the transistors i will describing them with the power terminals to the right closest to me
the ones who are upright in free air...
there is the front row (closest to me) they all have 40V 3.25V 40V
the rear row (fartest to me) they all have 1.8V 41V 1.2V
I notice halfway that some reads negative and some reads positive voltages... i didnt take note at first so i will simply write the voltages ... hope this is not that important
after that the transistors under the heatsinks and fans..
the 8 big transistors are on my left...
they are a batch of normal transistors with TO-220FP casing aroung the bigger ones
they all read 1.7V 1.7V 1.0V and there are others wich are smaller and almost square with foam pads underneath them.. they all read 1.2V 35V 0.6V
then on the right there is a bunch of TO-220 transistors and 2 TO-220FP...
the 2 TO-220FP's legs looks weird... they are satinated not mettalic (like al the TO-220 on the right..) thats ok but they look kind of semi dark black (like when there is a short but no signs of shorts) anyways.. for those 2.. one reads 30V 0V 15V (the one the fartest of me) and the one closest to me reads 0V -25V -15V
then my partner noticed 2 of the big transistors Q118 and Q119 getting hot and what seems to be the transfo starting to wine a little we unplugged the amp and let it cool... now when we power the remote this sound is always present as soon as the amp gets the green light (after the 2second red OVL light) and the 2 big MJL3281A gets hot real quick... so we measured those 2 real fast and i reads
1-2 0 ohm
1-3 0.3ohm
2-3 0ohm
and the other
1-2 20k and lowering (capacitor)
1-3 120ohm
2-3 9.4Mohm
did we ****** something up removing the heatsinks and powered it for like not even a minute.. nothing seemed hot at first then all of a sudden thoese 2 gets hot and the transfo is winning a bit...
Well good job so far.
The DC voltage present on your speaker terminals tells me that all four main amp channels are working, albeit some better then others. The higher the DC offset the more leakage and aging issues the semiconductors in those channels have endured.
The MJL3281A that reads 0 and 0.3 ohms is shorted out very badly, this will cause the overload detection circuitry to trip and shutdown the power supply just after start up and it will cycle on and off in many cases. There are FUSE resistors on this transistor, they are blown or your 12 volt power supply would be blowing fuses and shutting down. Remove this device by simply cutting its legs off, and then re test the voltage issues. The channel that changes was the one with the blown output. This channel will consume most of our attention so finding it by this simple removal will help you.
As for the transistors getting hot: There are four little pot in each channel, I mark their current position's with a marker and turn them all counter-clockwise. This shuts down the output bias'ing and takes the amp to base current draw conditions, as the outputs are not bias'ed on. Remember to use a marks-a-lot to mark them before turning them backwards to their minimum positions. You will need to know approximately where they belong later on as you go thru re-biasing the amp channels back into operation. I use the history mark as a reference only as I setup all the channels back to proper bias using a meter and a few other tools you will not have on hand.
Reads positive and negative: Yes this means something since the amp has both a positive supply and a negative supply. So yes the polarity is important. There will be three supply rails to be concerned about...1: the +&- 15 volts supply feeds all the op-amps on the input crossover board, and the two on the main board. 2: the +&-41 to 42 volts supply for the output stage. And 3 the +&- 49 volt supply for the first two stages of the main amp. Remember PG operates there output stages at about 7 to 9 volts less per rail then they do the rest of the main amp. The main amp is the section that does not have ANY IC's in it, it only has discrete transistors. The term main amp channel has been used since the early 70's when I was learning about this stuff in school. I am too old to change now lol..
I am sure you have a blown channel, and its the one that reads 0 and 0.3 ohms on the meter. I cut the legs close to the transistor case to get it out of the way, as you will need to start metering the little green and grey resistors nearby. These are fuse resistors and they blow open inside and you will not see any clue they are blown until you ohm then out... As for transistor lead colors well some leads are tinned and some are just steel alloy, it really varies by manufacturer and spec, and unless you see the device literally blown up and burnt black the lead colors are just misguiding you.... Its late so I will stop here for now, and come back tomorrow after I get back from a appointment.
Have you read any of Perry Babins threads here on the DIY ? I suggest you look at any of his threads and then hit the links under his post to check out his great training site. I recommend it highly as much of it will help you to achieve your goal of repairing this amp on your on with just advise type help for us here on the forum... I'll be back tomorrow...
The DC voltage present on your speaker terminals tells me that all four main amp channels are working, albeit some better then others. The higher the DC offset the more leakage and aging issues the semiconductors in those channels have endured.
The MJL3281A that reads 0 and 0.3 ohms is shorted out very badly, this will cause the overload detection circuitry to trip and shutdown the power supply just after start up and it will cycle on and off in many cases. There are FUSE resistors on this transistor, they are blown or your 12 volt power supply would be blowing fuses and shutting down. Remove this device by simply cutting its legs off, and then re test the voltage issues. The channel that changes was the one with the blown output. This channel will consume most of our attention so finding it by this simple removal will help you.
As for the transistors getting hot: There are four little pot in each channel, I mark their current position's with a marker and turn them all counter-clockwise. This shuts down the output bias'ing and takes the amp to base current draw conditions, as the outputs are not bias'ed on. Remember to use a marks-a-lot to mark them before turning them backwards to their minimum positions. You will need to know approximately where they belong later on as you go thru re-biasing the amp channels back into operation. I use the history mark as a reference only as I setup all the channels back to proper bias using a meter and a few other tools you will not have on hand.
Reads positive and negative: Yes this means something since the amp has both a positive supply and a negative supply. So yes the polarity is important. There will be three supply rails to be concerned about...1: the +&- 15 volts supply feeds all the op-amps on the input crossover board, and the two on the main board. 2: the +&-41 to 42 volts supply for the output stage. And 3 the +&- 49 volt supply for the first two stages of the main amp. Remember PG operates there output stages at about 7 to 9 volts less per rail then they do the rest of the main amp. The main amp is the section that does not have ANY IC's in it, it only has discrete transistors. The term main amp channel has been used since the early 70's when I was learning about this stuff in school. I am too old to change now lol..
I am sure you have a blown channel, and its the one that reads 0 and 0.3 ohms on the meter. I cut the legs close to the transistor case to get it out of the way, as you will need to start metering the little green and grey resistors nearby. These are fuse resistors and they blow open inside and you will not see any clue they are blown until you ohm then out... As for transistor lead colors well some leads are tinned and some are just steel alloy, it really varies by manufacturer and spec, and unless you see the device literally blown up and burnt black the lead colors are just misguiding you.... Its late so I will stop here for now, and come back tomorrow after I get back from a appointment.
Have you read any of Perry Babins threads here on the DIY ? I suggest you look at any of his threads and then hit the links under his post to check out his great training site. I recommend it highly as much of it will help you to achieve your goal of repairing this amp on your on with just advise type help for us here on the forum... I'll be back tomorrow...
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