Orion HCCA amp parts substitution question

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I'm repairing a few orion amps. A 250 HCCA, 225 HCCA, and a 275 SX.

All three of them have shorted outputs and shorted power supplies. I have on order irf3205's to replace the smps60n06 fets in the power supply. Must any changes to the gate resistors be made?

For the outputs, I ordered original 2n6488/91 parts, so no changes made. I'll be replacing all mpsa06/56 drivers since I have plenty in my parts bin. I'll order mpsu07/57 if needed.

What is the rail voltage on these amps? I'm assuming the 275sx has the highest since it makes the most power at 4 ohms followed by the 250 and the 225. Can I replace the rail caps on the 225 with 35v versions of higher capacitance? I will keep the 50 volt versions on the 250 and 275.

They all use 10 ohm gate resistors so no changes will be necessary. Don't forget to check the 10 ohm resistors between the A56 drivers and ground in the power supply.

As long as the voltage rating on the capacitor is equal or greater than the originals, they will be OK.

If you don't know the rail voltage, find the Zener connected to the base of the 2n6488 standing vertically in the power supply. The rail voltage is ~1v greater than the Zener voltage.

If you have a couple of good FETs, solder one in each side of the supply and power it up (after removing the shorted outputs). Then you can measure the actual rail voltage.
Thanks Mr. Babin. With the fets installed, each resistor was measuring right at 10 ohms. I was thinking I would need to replace them with 63 ohm resistors to use the irf3205. Maybe I was thinking MTX power supply.

My plan is to strip all the fets and outputs, wipe down the board and replace the drivers. These amps are relatively old and one has minor corrosion, hence the wipe down. This will make it easy to fire up the amp with minimal fets to measure the rail voltage.

The 275SX is actually in a 225 case and an attempt at converting it to a 225 is next, but before I start rewinding toroids and adjusting rail voltages, I want to get it working first.

I have most parts on order. In the meantime, I can start stripping the boards down.

What's a good replacement for the double sided tape used on the transistor claps? I was thinking something along the lines of weather strip instead of double sided tape. That stuff is difficult to remove. Some transistors cracked when I removed the aluminum bars, but those were the ones that were shorted because once I took them off, all the shorts were gone. :xeye:
I use double-sided tape but I don't remove the backing so it can't stick to the transistors. When you burn the amp in, you need to re-tighten the clamps several times as the amp heats up and the tape compresses.

You could try to find some high-temp silicone rubber. http://www.mcmaster.com/ part number 93755K51 (or something on that page) should work well but I've never tried it.

To clean the boards, you can put them in the diswasher (don't use heat to dry them). I spray the boards with 409 and use a low pressure, pressure washer. Use compressed air to force the water from under the caps and ICs. If it's a warm day, set them in the sun to dry.

You can remove the pots before washing or flush them with contact cleaner after washing.
I already have a couple rolls of double sided tape so I'll use that with the back on. I thought about doing that, but I figured the wax paper used for backing wouldn't hold up.

Dishwasher to clean boards? I never would have thought of that, much less actually done it. At work we have some really potent contact type cleaner which dries damn near instantly. It leaves the parts cold as it dries, which sometimes leads to condensation. I have used this stuff to clean smaller boards and it does a good job, but it tends to eat away at certain plastics and removes markings off some components.
I pulled all the parts off the circuit board of the 275sx and cleaned it up a bit. The input power inductor is toast and I have some magnet wire on order to rewire it.

There are 4 main caps in the power supply primary. Two 1000uf 35V from b+ to ground BEFORE the inductor and two 3300uf 50V from b+ to ground AFTER the inductor.

Is there a reason why orion chose 35v and 50v caps for these locations? I was under the assumption that these were the smoothing caps, but those are on the audio side of the board and consists of 4 1000uf 35v caps and a couple smaller ones.

I'm thinking I can replace the 1000uf primary caps with 2200uf 25V units and the 3300uf caps with about 5600uf 25v caps as well. Is there a reason I shouldn't do this?

The board is pretty much bare at the moment so these mods should be fairly easy to do. The mpsa06/56 drivers in the PS have been changed already and the 10ohm resistors to ground all check ok.
All else being equal, higher voltage caps generally have lower ESR and will run cooler when there is significant ripple current. When you choose replacements, choose caps with the lowest ESR/impedance you can find. You should also use caps rated to operate at 105C (on the primary side of the power supply).These have worked well for me.

If you can't find a source for the 3300@50v axial caps, Radio Shack generally has them. I don't like buying replacement parts from RS but I haven't had any problems using these for repairs.

If you're going to reuse the old inductor core, you should scrape it smooth and dip/coat it in epoxy.
I already cleaned the inductor core up since it was all crusty from over heating.:hot: Should I wind it and dip it or dip it before winding?

For capacitors, I have a few on hand and a few on order of different ratings and voltages. If I can fit a higher uF cap, I'll give it a try. If they blow up, I'll use originals. I didn't pay much attention to the esr when I ordered the caps. I was having a hard enough time finding the right size since I couldn't source any locally (I now live in Cyprus).

FYI, I installed two fets and the rectifiers and the sucker powered up just fine without the input caps. I installed a jumper where the inductor would normally be and the PS buzzed a little, but I didn't have any caps installed in the primary side. It was a really faint whine. I measured the rails at +/- 29V. This is for the 275SX.

Also on order are a few strips of high temp silicone to replace the double sided tape.

This hobby gets expensive fast. A few fets here, some outputs there, it all adds up. Of course, I'm ordering enough crap for 3 amps. The 250 alone uses 18 fets in the PS.
ECM said:

This hobby gets expensive fast. A few fets here, some outputs there, it all adds up. Of course, I'm ordering enough crap for 3 amps. The 250 alone uses 18 fets in the PS.

This sounds more like a restoration than a repair, but should be some very nice amps when done. What do you do write down all the parts, or do you have the schematic for them?
jol50, yes, it does sound more like a restoration.

I bought all three amps non-working. On all three, it seems the output section shorted, then took out the PS.

Instead of just replacing the shorted parts, I'll be replacing them all since they were all subjected to the same abuse that caused the shorts in the first place.

I don't have a schematic for them, but folks on this forum are more than willing to help out. Especially Perry Babin.

I have repaired amps on and off for about 12 years and I have been lucky enough to be able to repair all but one (it was an Xtant).

I plan on keeping these for myself, so I'm going all out on the repairs. I plan on installing better power supply fets, larger caps, etc. It probably won't make a sonic difference, but it gives me peace of mind.
I have not done that much of this, but I do one part # at a time on the board so I don't screw something up. Just wondered what you do if you take a lot of things out at once...or the proper way.

Maybe some time I would do a project like that, the broken amps I have now are newer and not that good except for the alpine 1002 I posted about. Unfortunately it is a little beat up on the outside. But then I don't worry if I can't fix them either. Trying to get a little HK that might need a workover, that would be a nice little amp I'm told...if I can fix it.
I write down all the component locations before removing them. In the orion amps, like half the board contains power supply fets so it's no biggie to remove all of them at once. Before I remove the outputs, I make a quick reference sheet with component part numbers and locations.

Sometimes, if i get an amp that is missing parts, I'll try to match up the missing parts with the parts on the other channel. that usually works for me.

Ampguts is a good website with lots of internal pictures that you can use for reference. If all else fails, you can ask on this forum.
I'm still working on the 275SX. I epoxied the inductor core and rewound it. No shorts between any of the coils or to the inductor core itself (I made a small dmm probe incision to the metal on top of the core).

I replaced the capacitors on the power input side and installed a couple fets. It worked, but made a faint whine. I installed all 10 fets and it still works, but it is still making a faint whine. Is this normal? I recall someone on this forum said the toroid will make noise with no load and that they could actually hear music coming from it.

I'm going to install a pair of outputs per side and go from there. I'm at work, so I don't have a speaker handy, but I'm curious to see the amp work.

Even though I am getting +/-29V on the rails, the power light does not come on. I haven't tested the LED so it might be burned out.

Quick side note: My "faulty" DC power supply works just fine. It just doesn't like MTX amps. With the orion amp, it maintains a steady DC output.
I see, yes I know ampguts well. I could send them some pics too.

At least it is running. Had one amp I could hear static from the toroid, the rest I don't. Many have culk globbed under them, looks like for deadening...yet some don't.

Ran the alpine with one power mosfet in bad ch and it lives too. It is like two amps in one, so looking at the other channel is like a mirror even in power supply.
clipped, i think 36v would be high for a 75 watt/chan amp. I will double check the regulator zener to verify the value. The current draw at idle is very low...maybe 1/2 amp or so. This is exactly what the owners manual states. I'll be installing the rest of the outputs today and connecting a speaker to it.

I'm surpirsed the 250 has a rail voltage of 22v, the same as the 225. I'm led to believe 29V is about right for the 275 since the power supply caps are rated to 35V and I don't think the designer would run the rails at 36V with 35V caps. BTW, did you ever convert the 225 to 275 after all?

jol50, i was thinking along the same lines as you about the toroid. I'm going to put some epoxy on it to secure any loose coils that may exist. It's a very faint whine/buzz that is probably not audible once the bottom cover and side panels are installed.
hmmm.... good point and a good thing i didnt convert the 225 to a 275 if the rail voltage is indeed 29 volts...be sure to let me know, once you read the zener.

i was really surprised too when i measured the rails on the 250,
i guess after this i just assumed the 275 was 36 volts, as the 2150 is 36volts.

i still havent done the conversion yet cuz i havent had a need for it yet, my newest craze these days is finding good donor subs then rebuilding them to hit harder...ive found a few good gems out there, in need of a little tlc ,different spiders and epoxy in the right places.

In this post, the rail voltage for a 275hcca is 29 volts. The difference between a 275sx and hcca is the current delivery. The hcca uses more fets to deliver more current, but the rail voltage is what determines the power output, in this case 75 watts per channel. So I'm pretty confident the power supply in my 275 is working as it should.

All fets have been installed along with all the outputs and the amp is working like a champ. My power supply delivers no more than 5 amps and I'm using a pair of 4 inch speakers to test it and the amp sounds great. At moderate volume, it draws about 3 amps and hits 4amps on musical peaks.

Offset voltage at the output is 18mv and 11mv per channel.

I'm not going to call this a success until I use a proper power supply or battery to fully burn the amp in with some better speakers.

Thanks to all who pitched in and helped me fix it. I'm waiting on some parts before I can start repairing the hcca amps.

Clipped, what kinds of subs to you repair? do you wind the voice coils too?
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.