Orion 275 XTR noise

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When I run this amp on the bench using a battery, it works great. When it's powered by the car, I get terrible alternator whine and general noise.

The same RCAs, power and ground have no problem on any other amp, so the problem seems to be internal to this amp.

I doubt there's a schematic available, but if anybody knows of one, I would like to see it. Also, any suggestions would be appreciated. Since its pretty old and recently bought used, I suppose I should go through and replace the caps and transistors...what else is commonly replaced on a rebuild?

Unfortunately, I don't have access to a scope right now so I'm kinda shooting in the dark. I've built and repaired headphone amps, but never car amps...thought I would query the experts here.

Also any experience here with the older Rockford Fosgate 360.6 amps? It looks like a nicely built amp, but before I go through the trouble installing it, any opinions on it for an SQ install...particulary compnent quality and simplicity of design/ease of repair?

Thanks in advance!
 
resolder the rca connectors that are on the board...not only the connection to the board, but the actual outer barrel ground joint to the frame of the connector both inside and outside.

id go over the pot joints (no pun intended) one more time too, make sure the irons hot.

and if its a pioneer headunit your using, ground the rca cable shield to the radio chassis.

pioneers have a way of blowing the rca outputs when you unplug them without turning off the radio first.
 
Thanks for the tips. I finally got the amp all apart, resoldered the points you suggested along with some other large solder points.

There are four 1000uF 25V caps near the rca jacks that have some white powder around the solder points -- I don't know if its corrosion or leached electrolyte. Also there are two large 3300uF 35V caps that are a bit bulged at the top. I'll go ahead and replace all the electrolytic caps, as I know they have a limited useful life.

Are the FETs, transistors, and IC's normally replaced as needed, or replaced en masse on a typical rebuild?
 
if you can find Elna RJH series caps, they have low ESR and are rated for 105 degrees.

usually all the outputs should be replaced for each set per channel...

eg:in a 225hcca there are 3 + 3 for each channel, if 1 in the set of 3 are damaged, id replace all in that set...im not sure of the part number of the xtr 275.

the Digital reference and SX series used 2n6488/91...you can use BD909/910 for replacement also the BD911/912...the 911/912 have a higher voltage rating, and no it wont increase the power using a higher rating.

the 2n6488/91 are rated at 75 watts each, the BD are rated at 90 watts each.
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for the power supply fets id replace with IRF3205, recommended by Perry in the past, and verified by me replacing all the fets in four 2150sx amps and almost all other amps ive repaired.

check the resistors going to the +/- legs of the opamps too, when they go it will cause the amp to put out DC if they fail.

if you have a big 1-2 ohm 50 watt resistor install it 'inline' with the positive batt wire, measure the voltage across the resistor (one lead on each end) and divide the ohm of the resistor by the voltage reading across the resistor, this will tell you the idle current ...it shouldnt be any higher than 2-3 amps....

if it is higher then you more than likely have a bad output or fet somewhere...then you would know whether to change any of them.

also a good idea to check the vertical drive transistors, these can be really misleading when diagnosing a blown orion...and will probably be the last set of semi's you check, after checking the outputs and fets.

so check if there is any DC on the outputs (no more than .050) then check the idle current...if alls good, you probably dont need to change any of those semi's or check them.

oh yeah, and check the rectifying diodes.
 
Great information -- thank you very much!

The 275 does indeed use 2n6488/91, and the recommended replacement part number for the ps fets is much appreciated -- I was having a hard time sourcing direct replacements through mouser or digikey based on the imprinted code.

I'll post results of my testing and reparations when they're done in case somebody else can get some use out of what I'm learning here. Thanks, Clipped, for the assistance!

While I'm ordering up parts, are there any other upgrades often done to Orion amps? In my experience with headphone amps, it was always fun trying different tubes and opamps to get slightly different colors to the sound...though that's much easier to observe with headphones.
 
the 225 hcca uses jfets in the soft start/muting circuit...but its a totally different design from the xtr275.

when the soft start/muting circuit malfunctions, you will get very little to almost no output.

the first two letters for the jfets are 2N**** i cant remember the whole part number. but you can identify them because the square pad on the pcb is on the other leg, theyre the little semi round transistors and shoud only be a couple of them if they use the same design in the xtr series.

the 225 hcca responds to capacitor value change (the big vertical ones), but the 2150sx and 250 hcca does not...the highest i went with the values were 1200, 1800, 2200...each step made the bass tighter, but that isnt neccesarily a good thing for fullrange sound

I tried the elna RE3 2200uf caps and didnt like them...made the amp sound fuzzy.

just over the weekend i discovered something i always thought was voodoo - rca cables, i have a really picky customer... that was complaining about the sound stage dropping.

turns out he bought some 4 element microphone cable from somewhere and had them make rca cables out of them...so we tried 4 different types of cable and each type had a different sound characteristic to them...

we tried

1.four element microphone cable
2.shielded coaxial with stranded core - copper
3.non shielded coaxial with solid core - silver/copper mix
4.typical chinese rca cable with no shielding and stranded core

and they all sounded different...the head unit was a denon z-1 alpha one proccessor from japan...so the detail was there.

may not have heard the difference with a cheap unit.
 
No -- the pcb pads at the RCA solder points showed no sign of significant stress...I didn't notice any pin movement when I resoldered, but I had a metal rca plug plugged into the jack to stabilize it as well as act as a heatsink. I also used a fairly precise soldering station with the heat just high enough to re-flow the solder, so it set pretty quickly. I'll inspect the integrity of the jack in more detail.

I did read out continuity between the poles of the rca jack, but not resistance between the shield and the speaker terminals -- I'll measure that when I get home this evening.
 
Orion 275XTR noise

If you would like to have your XTR275 serviced contact robotunderground@yahoo.com, they have serviced several amplifiers for myself as well as my customers and always get the job done right, NO switching out for cheaper parts.

As far as the Rockford 360.6 goes I just installed one last week! It's running 2 Cadence 6.5" components front & rear and an Audiobahn 15" sub. This amp is WAY under rated at 30 watts x 6. I highly recommend this amplifier for SQ, in an every day driver application!!!
 
Thanks for the info Travis -- I appreciate it.

I'll keep the repair shop in mind, but I'm really just trying to fix this out of interest in amplifier design and repair, and electronics in general. It's too nice of an amp to leave it unused, but if I somehow destroy it in this attempt I'll count it as tuition towards my education ;-)

Perry -- thanks for jumping in on this thread. I followed the links in your sig -- I have use your site before as reference...nice to have your help here! Come payday (tomorrow), I'll order your amp repair tutorial -- it's the least I can do for all the work you've put into the free information on your site and the help you provide on this forum.
 
I would expect both of the non-bridging wires to be directly connected to the shield of the RCA input jacks.

If you only use the right channel, do you have noise?

If you connect a jumper between the non-bridging speaker terminals, does that reduce the noise level?

If someone else here has a similar amp that they're not using, please measure the resistance between the input RCA shields and the non-bridging speaker terminals to see if there is essentially 0 ohms between them.
 
Probably foolishly, I had already begun removing and replacing capacitors, so I wasn't able to test one channel vs the other wrt to noise.

All electrolytic caps carefully replaced (no major issues to report), the amp powers on but no speaker output on either channel. Heh...on to the next problem!

I'll do some additional testing and post more information when I have it.
 
I'm now reading essentially 0 ohm from rca shield to R+ and L-

Not sure if changing caps made the difference or if I was just not getting a good connection with my probe on the L- measurement previously.

Still not getting *anything* out of the speaker leads -- not sure where to begin with that since it was working before I swapped in new caps. I'm just now getting into Perry's tutorial (highly recommended!), so hopefully I'll be able to stand on my own two feet a little better in the coming weeks.

Thanks for all the help!
 
The first hing you need to do is confirm that you have supply voltages on all of the ICs and output transistors.

The 8 pin op-amps should have positive 15v on pin 8 and negative 15v on pin 4. The 14 pin op-amps should have +15 on pin 4 and -15 on pin 11.

If this amp has an 18 pin IC in a socket, it should have 5v on pin 14.

Does this amp have a similar set of chips as the 600.4?

The folder is
repair_tutorial/miscellaneousstuff/orion/orionxtr600pt4

Double-click the file
repair_tutorial/miscellaneousstuff/orion/orionxtr600pt4/orionxtr600pt4notes.htm

If possible send me a set of photos for it.
 
Here's the board in its entirety.
DSC01196.jpg


Not a great picture, but the best I can get at the moment.

The three opamps, two are 4562D and the one closest to the top of the picture is a 5532D. Input voltage is 12.35V, 5532D reads -14.18 at pin 4, and 14.73 at pin 8. 4562D both read -14.07 at pin 4 and 14.62 at pin 8.
 
They are in place, although you bringing this up made me focus on that area. The configuration of the modules and jumpers was essentially the factory configuration, except with a single jumper on the middle pair of pins. According to the manual, this jumper activates summed mono operation.

After removing this jumper, the amp works fine on the bench -- I get sound out of each channel and out of the bridged channel. Installing the jumper cuts all speaker output once again. So it looks like there's some problem with the circuit responsible for internally summing the signal.

I'll install this in the car and see if the work done so far fixes the noise problem I was having originally.
 
Still some noise when installed in the car, although now I can eliminate the noise by jumpering the RCA shield to one of the non-bridging speaker out terminals.

I'll pull it out and take apart the rca connectors to see if I there's a problem with them. Any idea where replacement parts can be found? I can rebuild the 4-RCA block, but I would rather buy a new one if it there's a source for them.
 
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