Pioneer SA-9100 Tone switch fault

kwape

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Just purchased this amp through a trade in BT. It is all original but has had the amp section serviced in years past. The issue is with the pre-amp section; Flipping the tone switch on causes a loud pop and the tone switches (bass & treble) are not functional. I just started looking at this but I would assume I have a faulty transistor. The pre-amp is also a bit noisy. I separated the unit to confirm this.

pre-amp board AWG-018 already has 2SC2240 transistors subbed in, pulled one and tested good. The rest look to be original on that board. Maybe one of the EQ/tone boards?

I have a caps list ordered and I see there's already some reputable parts lists made for this unit. I have many of the equivalent transistors on hand. Not going to go off subbing transistors for no reason but I might as well sub the 2sc1345 with ksc1845 on the filter board (they all tested good), maybe it will help the noise. This should be a pretty simple fix if I can narrow it down a bit.
 
Sounds more like a leaky capacitor is letting DC get on the tone board and causing the POP when you flip the switch, but it's definitely a good idea to get rid of the known troublemaker transistors throughout the amp while you're in there. If you don't do it now you'll be going in again and again as they crap out.
 
started the recap and no longer getting a loud pop using the tone switch, subbed 2sc1345 with ksc1845. Still was getting some static using the bass controls but will likely be alleviated by the time I'm through. Amp is also much quieter.


on the power supply circuit A AWR-031 schematic & parts lists have 470uf 63v capacitors while my amp has 2200uf 80v caps. Wasn't paying attention when I ordered these 2200uf 100v caps, they're too long. damn shame they're nice caps. I can just fit 35.5mm in length with these caps @ 63 volts http://www.mouser.com/Search/Produc...HDvirtualkey64700000virtualkey647-UKW1J222MHD Or should I opt for the 470uf that is listed in the schematic?


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That's a pretty huge uf difference, you should always go with what's on the board and you should never go under the voltage rating of the existing cap. I would ask over in the Pioneer forum, in fact I'd suggest contacting a moderator and ask to have this whole thread moved over to the Pioneer forum - you'll get some very experienced eyes on it that way. You're doing a great job so far, and that's a fine integrated well worth doing right :thumbsup:
 
yep that would be a snap-in. solves that problem.(2200uf 80v)

trying to figure what I should use for the big 15000uf 50v filter caps. They're 50mm (2") X 73mm high. A real pita to find a sizeable replacement. I don't think buying smaller clamps for a 40mm dia cap would fit existing mounting locations. heres' a couple options I was looking @:

Nichicon KG 15000uf 50v 40mm x 80mm. (will need to fill that 10mm dia. 80mm height is the max that will fit.....I think)
http://www.partsconnexion.com/capacitor_ele_nichicon_kg.html#18367

Mundorf 15000uf 63v 35mm x 60mm. Mundorf sells a 35mm-50mm adhesive pad for these caps that would make a clean look.
http://www.partsconnexion.com/capacitor_ele_mundorf_plugin.html#20997

Would like to see what others have used,and is there anything better than tape to increase diameter to fit clamps if I went with nichicon?
 
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I've heard of some folks using foam pipe insulation or weatherstripping but I'm not sure how it would look. Seriously I would check the Pioneer forum, I think Mark (markthefixer) and/or Glen (echowars) have come up with a solution for that (different clamp available from Mouser maybe?) l think all this has been covered at some point over there.
 
ok thank you. I'll do more searching.

On the parts lists I've seen people using Vishay screw terminals @47+$ each
 
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Coming along with this recap. I still get a pop on the left channel if I'm not gentle operating the tone defeat switch, but is working otherwise. I'm guessing it's the switch, when I operate it gently there's no issue. Already has been given a deoxit D5 bath, perhaps some solvent free F100 fader lube will help. I have a new relay I still need to put in, and waiting on 4 caps to arrive that I ordered the wrong dimensions to (2200uf 80v & 6.3v 330uf). I do have a service receipt for this unit showing the 2200uf 80v caps were replaced in 2007 by a tech, but I'm still not completely sure if the originals are the same value.

I would guess I spent $230 just in parts for this unit. The big filter caps are 47$ each. And I was experimenting with trying to use as many Nichicon KZ (muse) caps as possible. They're much larger than KA, FG or KW caps and don't fit everywhere. I also used many Wima film & Nichicon KL (low-leakage) where applicable. Granted I would buy 10+ units of these items when discounts are available, it's still not cheap.


just the relay & 4 caps left to change and this should be done, unless something comes up.

You may note some sloppy work around the left channel amp board wire wraps. That would be from the tech who serviced this unit previously. I have receipts from the original owner of a couple tech visits. They really butchered the wire wraps, 2 snapped off. Replaced with some solid core wire, tightly wrapped with pliers and soldered on. I'm now going to make an effort to buy a wire wrap tool, even though they're 40-60$. I prefer to unsolder the posts but doing so is very time consuming.


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Might want to double check your DC offset, idle current and power supply voltages - sounds like something might be out of balance. This is why it's a good idea to go through the entire amp section by section and replace all of the known troublemaker transistors, particularly in the power supply, power amp and pre amp sections. It'll prevent you from having to go back in over and over again to chase down mystery problems plus it will help lower the noise floor. Lots of great rebuild advice for this sweet amp over in the Pioneer forum.
 
yeah I was just thinking that. I set the bias & DC offset, but I remember the DC offset was acting funny on the left channel. I was getting some DC at the terminals with the channel off. I just didn't want to go off changing all transistors without it being necessary. I changed a few known troublemakers, and many have been done already by other techs.


I had 2 10uf 50v caps that were open on the power supply B board (AWR 032). That might be a good place to look for faults.
 
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AWR-032
Power supply Circuit B

Pin 8: +42.8v
*Pin 3: -34.6v
Pin 10: +24.25v
Pin 11: +15.54v
Pin 4: -13.31v
*Pin 2: -22.69v

*Pin 5: -59.9v


Pin 6: -60.9v
Pin 7: +60.3v


The * are on the pins that are off
Pin 3: +35v
Pin 2: -16v
Pin 5: -42v


This board has been pulled and worked on previously. A couple transistors have been subbed; ECG153 for Q2 2SB507, ECG290A for Q4 2SA720. I'm just going to shotgun the whole board. Some resistors are looking ruff from heat. I also noticed the NPN side has way more heat (Q1 2SD313) that the PNP side, not sure if that's normal.

Why do service techs seem to butcher everything? Every project that has been worked on by a previous tech has had very sloppy work done; traces scraped to shit, sketchy equivalents, butchered wire wraps, no clean up.
 
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Completed replacing all components on AWR-032 power supply board B. Zener diodes were bad. That was really it, but now it is working better. It's producing even heat on both sides, and voltages prove it.

Voltages VDC:
pin 8: 44.2
pin 3: -25.51
pin10: 25.83
pin 11: 16.81
pin 4: -13.34
pin 2: -16.67
pin 5: -43.5
pin 9: 34.8

pin 6:-60.9
pin 7: 59.7

All these check out nearly spot on. But I'm still getting the same pop flipping the tone defeat switch. At this point all caps have been replaced, relay done as well(not that it matters). Any suggestions what to look at?

only the tone defeat does this......


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As to the switch, you may need to physically open it up and do the pink eraser trick to really mechanically clean the contacts.
 
thanks man I'll try that. I was thinking either disassemble the switch or the 2200uf caps on power supply AWR-031 were too big and should change to the 470uf in the schematic.
 
thank you for the eraser trick that took care of it. Switch was heavily oxidized and gummed up with deoxit. I also switched out the 2200uf caps for 470uf on AWR-031, I think the schematic is correct. I was feeling brave so I did the loudness switch as well. Will need to let it run for a few hours but so far its doing what it's supposed to.
:thumbsup:


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Nice work. I'm the original owner who traded this amp to Andrew. I started a conversation with a mod to get this moved to the Pioneer forum.

He also restored/recapped the amp I traded for. It sounds fabulous and looks like new. He made new blonde oak side panels for it and repainted the top metal cover with a hammered finish.
 
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Always good to see one of these fine amps getting the tlc that's needed to bring it back to it's best, well done.

I prefer to unsolder the posts but doing so is very time consuming.
I know it is easier to work on a board when it is out but on the 9100 all boards can be worked on relatively easily by cutting ties to loosen wires, removing heatsink etc.
 
everything's working well. Been playing it the past few days a few hours at a time with no issues.

tested the output on the scope @ 1khz sine wave into 8 ohms:

Left Channel: 84.5wrms

Right Channel: 83.2wrms

Thank you for aiding me in this project.

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I'm just currently having the protection issues that are renown in this amplifier rectified and a recapping and repaired, but it was wondering why the loudness switch has over 10 db of gain when pressed, is there someone that
has experienced this, for it certainly is a lot louder that most other receivers, with the button?
 
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