Orion 222 SX repair questions

grjr · 21st December 2007, 05:58 AM

Hi, I'm working on a 222 SX amp here and am not too familiar with it. Measured the voltage rails to be about +/- 16V, is this right? Seems low, but the 7812s and 7912s used for the OPAMP power supply seem to agree with the voltage rails (I'm guessing they would be 15V regulators otherwise). Also it appears that the switching transistors are BUZ11 MOSFETs, looks like the amp was modded to work with these. Right Now I have some DC voltage on the outputs and the clip or protect lights are coming on, one of the OPAMPs is running considerably hotter than the rest, think I will start there.

Clipped · 21st December 2007, 02:24 PM

not a 222, but i had a prolem with a 2150sx that had a bad mylar capacitor (or was it a tantalum, always get them mixed up) which was tied into the supply leg of an opamp and made it throw out a dc signal, the resistor connected to it was also bad.

another problem i had on a 225hcca was a bad resistor that was tied into one of the regulating transistors, causing it to put out only half of the waveform...simulating dc

id check to see if the outputs are putting out dc, positive or negative then you can track it from there.

ppia600 · 22nd December 2007, 02:05 AM

Quote:

Originally posted by grjr
Hi, I'm working on a 222 SX amp here and am not too familiar with it. Measured the voltage rails to be about +/- 16V, is this right? Seems low, but the 7812s and 7912s used for the OPAMP power supply seem to agree with the voltage rails (I'm guessing they would be 15V regulators otherwise). Also it appears that the switching transistors are BUZ11 MOSFETs, looks like the amp was modded to work with these. Right Now I have some DC voltage on the outputs and the clip or protect lights are coming on, one of the OPAMPs is running considerably hotter than the rest, think I will start there.

The voltage rails should be close to the large capacitor ratings on the output side of power supply. Also check to see if any of the outputs have direct shorts between the collector and emittor. Sometimes they're even shorted between the base and collector or emmiter. If you find a shorted transistor or more, remove them and power it up without them installed to try for the DC voltage again. Be sure to have the transistors clamped to the heat sink though to keep from frying the good ones.

grjr · 22nd December 2007, 02:54 AM

ok, so I've checked a few things out and the outputs appear to be good along with their drivers. The rail caps are rated for 25V, so I'm guessing the rail voltages are fine. I found a pair of bad MPSA56 BJTs along with a couple of open 2.7 ohm resistors in the power supply section, they appear to be part of the drive circuitry for the switching MOSFETs. I've also found a couple of bad 2N5639 MOSFETs that shorted Drain to Source. They are connect to the inputs of one of the OPAMPs. I don't have replacement parts on hand so I'll be waiting until I can get parts.

ppia600 · 22nd December 2007, 03:05 AM

Almost seems like only one side of the transformer is being switched so you may have found the problem there. There are several guys here who will be able to recommend the optimnum fets to use in the power supply.. and I'm not one of them. (lol) I've had to ask a few times myself.

Perry Babin · 22nd December 2007, 04:23 AM

If the 2.7 ohm resistors were in series with the collectors of the MPSA06 power supply drivers, replace the MPA06s also.

The rail voltage is set by the zener connected to the base of the 2N6488 standing in the supply near the transformer. There may be another diode in series between the zener and the base of the 6488. If the zener is a 15v zener, the rail voltage was correct. The 225 of approximately the same vintage had an 18v zener.

The amp will play without the 2N5639s (jfets, not mosfets). They are part of the muting circuit.

grjr · 22nd December 2007, 04:28 AM

hmm, I stole some transistors from another amp to power this one up, I am getting DC voltage at the outputs. I probed the outputs of the OPAMPs and they have DC voltage on their outputs so there is something wrong with the preamp section. I noticed some corrosion on the pins of the OPAMPs near the DIN connection. Any recommendations?

Perry Babin · 22nd December 2007, 04:37 AM

If you have all of the power supply voltages (±rail, ±regulated), look at the polarity of the voltage on the outputs of the op-amps in the power amplifier. If the polarity of the DC on the output is the same as the voltage on the output, it's probably being driven high by something in the preamp section. The newer amps have DC blocking caps between the pre and power amp sections. I'm not sure if these have them.

It should be easy to see where the DC offset enters the signal line. All of the outputs of the op-amps should be near 0v.

grjr · 22nd December 2007, 05:33 AM

Thanks, I'll do some more troubleshooting. Here's a couple pics of the amp for reference.

http://www.kernclassifieds.com/forumpics/diyaudio/

Perry Babin · 22nd December 2007, 06:13 AM

I've seen a lot of Orion amps but I can't remember seeing one with a green board.

The regulation appears to be different in the supply. Are the collectors of the A06 drivers connected directly to B+?

21st December 2007, 05:58 AM	#1
grjr diyAudio Member Join Date: Sep 2007	Orion 222 SX repair questions Hi, I'm working on a 222 SX amp here and am not too familiar with it. Measured the voltage rails to be about +/- 16V, is this right? Seems low, but the 7812s and 7912s used for the OPAMP power supply seem to agree with the voltage rails (I'm guessing they would be 15V regulators otherwise). Also it appears that the switching transistors are BUZ11 MOSFETs, looks like the amp was modded to work with these. Right Now I have some DC voltage on the outputs and the clip or protect lights are coming on, one of the OPAMPs is running considerably hotter than the rest, think I will start there.

22nd December 2007, 03:05 AM	#5
ppia600 diyAudio Member Join Date: Jun 2007 Location: Louis y ana	Almost seems like only one side of the transformer is being switched so you may have found the problem there. There are several guys here who will be able to recommend the optimnum fets to use in the power supply.. and I'm not one of them. (lol) I've had to ask a few times myself. __________________ Don't worry... you can always turn the gain down!

22nd December 2007, 04:23 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If the 2.7 ohm resistors were in series with the collectors of the MPSA06 power supply drivers, replace the MPA06s also. The rail voltage is set by the zener connected to the base of the 2N6488 standing in the supply near the transformer. There may be another diode in series between the zener and the base of the 6488. If the zener is a 15v zener, the rail voltage was correct. The 225 of approximately the same vintage had an 18v zener. The amp will play without the 2N5639s (jfets, not mosfets). They are part of the muting circuit. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

22nd December 2007, 04:37 AM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If you have all of the power supply voltages (±rail, ±regulated), look at the polarity of the voltage on the outputs of the op-amps in the power amplifier. If the polarity of the DC on the output is the same as the voltage on the output, it's probably being driven high by something in the preamp section. The newer amps have DC blocking caps between the pre and power amp sections. I'm not sure if these have them. It should be easy to see where the DC offset enters the signal line. All of the outputs of the op-amps should be near 0v. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

22nd December 2007, 06:13 AM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	I've seen a lot of Orion amps but I can't remember seeing one with a green board. The regulation appears to be different in the supply. Are the collectors of the A06 drivers connected directly to B+? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

21st December 2007, 02:24 PM	#2
Clipped diyAudio Member Join Date: Mar 2005 Location: home	not a 222, but i had a prolem with a 2150sx that had a bad mylar capacitor (or was it a tantalum, always get them mixed up) which was tied into the supply leg of an opamp and made it throw out a dc signal, the resistor connected to it was also bad. another problem i had on a 225hcca was a bad resistor that was tied into one of the regulating transistors, causing it to put out only half of the waveform...simulating dc id check to see if the outputs are putting out dc, positive or negative then you can track it from there.

22nd December 2007, 02:54 AM	#4
grjr diyAudio Member Join Date: Sep 2007	ok, so I've checked a few things out and the outputs appear to be good along with their drivers. The rail caps are rated for 25V, so I'm guessing the rail voltages are fine. I found a pair of bad MPSA56 BJTs along with a couple of open 2.7 ohm resistors in the power supply section, they appear to be part of the drive circuitry for the switching MOSFETs. I've also found a couple of bad 2N5639 MOSFETs that shorted Drain to Source. They are connect to the inputs of one of the OPAMPs. I don't have replacement parts on hand so I'll be waiting until I can get parts.

22nd December 2007, 04:28 AM	#7
grjr diyAudio Member Join Date: Sep 2007	hmm, I stole some transistors from another amp to power this one up, I am getting DC voltage at the outputs. I probed the outputs of the OPAMPs and they have DC voltage on their outputs so there is something wrong with the preamp section. I noticed some corrosion on the pins of the OPAMPs near the DIN connection. Any recommendations?

22nd December 2007, 05:33 AM	#9
grjr diyAudio Member Join Date: Sep 2007	Thanks, I'll do some more troubleshooting. Here's a couple pics of the amp for reference. http://www.kernclassifieds.com/forumpics/diyaudio/

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Old School Orion 2150 gx.I must repair this amp	spooney	Car Audio	99	21st August 2010 02:53 PM
Orion 280GX amp repair	thegmann	Car Audio	11	11th April 2008 05:44 PM
couple old school orion questions	Clipped	Car Audio	3	5th August 2006 10:09 PM
Orion Construction Questions	¿GotJazz?	Multi-Way	3	6th October 2004 04:44 PM
Orion questions	dayneger	Multi-Way	8	4th March 2004 09:28 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read