Orion HCCA 250r ground

ash4kel · 14th August 2011, 05:55 PM

Looking for a little help on what to look at next. I have a hcca 250r. When I bought the amp I had a bad power fet. I replaced the fet and everything worked fine. I then decided to replace the rest of the fets for consistency purposes. Now when I power it up I blow fuses immediatly. So I checked the resistance on all the fets and everything is consistant. I do not have a short between any of the legs and on one leg they all read .002 to ground. I believe that is correct though. I have continuity between the negative and the postive on the power. When I take that reading it doesnt immediatly jump to .002 to ground. It acts like it is reading through a transistor and goes from a higher reading to the .002 reading after a couple jumps on the fluke meter. Hope this makes sense. Thanks

Perry Babin · 14th August 2011, 07:45 PM

Is this the same amp that you've been working on?

ash4kel · 30th August 2011, 02:56 AM

Yes it is. Sorry I can only seem to get to work on this project in between all the other stuff that needs to get done so sorry for the long delay. I forgot that I had even posted about this amp before.

ash4kel · 6th September 2011, 11:29 PM

Still hoping for a little help. Also I was given a part number for the rca plugs for an HCCA 225r but when I went to the site, it wouldn't let me order just one. If someone has a site where I can order a replacement, that would be great. Thanks.

Dr Zeus · 7th September 2011, 01:38 PM

How large of a fuse is is blowing? Have you checked all the fets in this amp? Is there any sign of something heating up when power is applied?

Perry Babin · 7th September 2011, 02:01 PM

Find your old post and place a link to it here. That will help prevent repeating suggestions that were given earlier.

ash4kel · 8th September 2011, 04:53 AM

Sorry, but I'm not sure how to link my other posts to this post but I really hadn't gotten any other advice for this problem yet. Originally I had a bad BJT that caused a ground then found it and replaced it. It then worked fine. But on your advice ( Perry ) you said to replace them all to make sure it would be reliable ( by the way I agree with you ). Thats when this problem returned. But when I had the bad bjt before, I read a ground on the bad bjt but now I read them all consistently. See the readings I posted earlier in this post. I blew a 30 amp fuse. So now it's up to date on whats taken place. Sorry for the confusion. I hope you can still help. One more thing. On one of my posts I asked what bjt's went where just in case I had misplaced one or more. Perry responded and I had checked that I had put them in the correct order. Thanks again.

Perry Babin · 8th September 2011, 02:22 PM

There are two banks of FETs in the supply. One bank is from 33-66. The rest are in the other bank.

Set your meter to ohms and place one probe on the first leg of any transistor in the bank. Place the other probe on the first leg of each of the other FETs in the bank.

Do you read ~20 ohms for every transistor in the bank?

Do this for both banks.

Touch the leg of the transistor. Do not touch the solder pad for the transistor.

ash4kel · 10th September 2011, 08:43 PM

Yes I read ~20 ohms on each bank doing as you described.

Perry Babin · 10th September 2011, 11:51 PM

For each bank of power supply FETs, follow the traces that feed the gate resistors back to the two MPSA56s that drive them. The traces will go back to the emitter legs of the A56s. For each MPSA56, measure the resistance from the collector (leg 3) to ground. What is the resistance for each?

I think they're Q57 and Q59 but I'm not sure.

14th August 2011, 05:55 PM	#1
ash4kel diyAudio Member Join Date: Mar 2011	Orion HCCA 250r ground Looking for a little help on what to look at next. I have a hcca 250r. When I bought the amp I had a bad power fet. I replaced the fet and everything worked fine. I then decided to replace the rest of the fets for consistency purposes. Now when I power it up I blow fuses immediatly. So I checked the resistance on all the fets and everything is consistant. I do not have a short between any of the legs and on one leg they all read .002 to ground. I believe that is correct though. I have continuity between the negative and the postive on the power. When I take that reading it doesnt immediatly jump to .002 to ground. It acts like it is reading through a transistor and goes from a higher reading to the .002 reading after a couple jumps on the fluke meter. Hope this makes sense. Thanks

14th August 2011, 07:45 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Is this the same amp that you've been working on? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

7th September 2011, 02:01 PM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Find your old post and place a link to it here. That will help prevent repeating suggestions that were given earlier. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

8th September 2011, 02:22 PM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	There are two banks of FETs in the supply. One bank is from 33-66. The rest are in the other bank. Set your meter to ohms and place one probe on the first leg of any transistor in the bank. Place the other probe on the first leg of each of the other FETs in the bank. Do you read ~20 ohms for every transistor in the bank? Do this for both banks. Touch the leg of the transistor. Do not touch the solder pad for the transistor. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

10th September 2011, 11:51 PM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	For each bank of power supply FETs, follow the traces that feed the gate resistors back to the two MPSA56s that drive them. The traces will go back to the emitter legs of the A56s. For each MPSA56, measure the resistance from the collector (leg 3) to ground. What is the resistance for each? I think they're Q57 and Q59 but I'm not sure. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links


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30th August 2011, 02:56 AM	#3
ash4kel diyAudio Member Join Date: Mar 2011	Yes it is. Sorry I can only seem to get to work on this project in between all the other stuff that needs to get done so sorry for the long delay. I forgot that I had even posted about this amp before.

6th September 2011, 11:29 PM	#4
ash4kel diyAudio Member Join Date: Mar 2011	Still hoping for a little help. Also I was given a part number for the rca plugs for an HCCA 225r but when I went to the site, it wouldn't let me order just one. If someone has a site where I can order a replacement, that would be great. Thanks.

7th September 2011, 01:38 PM	#5
Dr Zeus diyAudio Member Join Date: Oct 2010	How large of a fuse is is blowing? Have you checked all the fets in this amp? Is there any sign of something heating up when power is applied?

8th September 2011, 04:53 AM	#7
ash4kel diyAudio Member Join Date: Mar 2011	Sorry, but I'm not sure how to link my other posts to this post but I really hadn't gotten any other advice for this problem yet. Originally I had a bad BJT that caused a ground then found it and replaced it. It then worked fine. But on your advice ( Perry ) you said to replace them all to make sure it would be reliable ( by the way I agree with you ). Thats when this problem returned. But when I had the bad bjt before, I read a ground on the bad bjt but now I read them all consistently. See the readings I posted earlier in this post. I blew a 30 amp fuse. So now it's up to date on whats taken place. Sorry for the confusion. I hope you can still help. One more thing. On one of my posts I asked what bjt's went where just in case I had misplaced one or more. Perry responded and I had checked that I had put them in the correct order. Thanks again.

10th September 2011, 08:43 PM	#9
ash4kel diyAudio Member Join Date: Mar 2011	Yes I read ~20 ohms on each bank doing as you described.

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