xXColdShotXx

Active Member
I hooked the spec 2 up a while back and let it play for around 10 minutes, then all the sudden I hear a small pop and smell something get hot, then I noticed the right meter was almost on 500 and the protection light was on. I had a yamaha cx-600/u pre-amp hooked up to it and it was playing just fine on both channels until that happened. Anyone have any suggestion what to test first? I want to do a temp fix until I get all the caps and stuff replaced. If possible I'd like to get it going without needing a oscilloscope, audio analyzer or 4/8 ohm dummy loads.
 
See if you can identify what part smoked and then start from there. if one channel is still okay, use that as your comparison. You can use your DMM in resistance test mode to find these faults. read up on the spec2 repair threads.
 
RL1, the single reed relay is an achilles heel in the design.

more to come later...
 
As MTF is compiling the list of things to check and order I'll let you in on the work it will take to repair.
You'll probably want to take care of the good amp board as well.
The Spec 2 is fairly easy to access. The amp boards and heatsink can be removed as an assembly. Then, they can be worked on the bench.
I would restore each amp board along with the reed relay work-a-round.
About 6-8 hours of work. Not a bad job, if one has the skills and tools.
Also:
The power supply rebuild should probably should be considered.
The meter board has tons of the problematic transistors and Tantalum caps.
Add a few more hours for the rest of the restore.
 
I found this past post:

I wanted to post this before for I forgot:
I used a Littlefuse HE751A2400 for the R1 relay that we "Dead Bug" mount.
Mouser Part number:
934-HE751A2400
It mounts a little better due to the wider back of the IC style relay. I used hot glue to fasten it.

The old part number is obsolete.
 
I already have enough caps, transistors, diodes and 3 relays for the spec 2. Here's the list of stuff I actually have. Some parts I have extra since my SX-1250 takes some of the same parts.

647-UKL1H4R7KDDANA | 2
647-UPW1H100MDD | 8
667-ECQ-E2106KFB | 1
647-UPW1H220MDD | 4
647-UPW1A221MED | 4
647-UPW1A471MPD |<- don't have 647-UPW1C471MPD | 2 <- using these instead
647-UPW1E471MPD | 1
647-UPW1H471MHD | 1
647-UPW1H102MHD | 1
80-F612JF224J063A | 2
505-MKS2C041001FJC00 | 4
512-KSA992FBU | 12
863-MJE15032G | 8
863-MJE15033G | 4
512-KSA733CYTA | 5
512-KSC945CYTA | 5
512-KSC2383YTA | 2
512-KSC2690AYS | 2
512-KSC2073TU | 1
512-KSA940TU | 1
652-3386H-1-501LF | 2
652-3386H-1-101LF | 6
512-1N5247B | 4
653-LY2-0-DC24 | 2
653-LY2-DC48 | 1
661-E36D101N223TDB7M | 4
934-HE3621A2400 | 2
 
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If I rebuild all the boards I don't have a way to set the 4Ω and 8Ω loads and distortion. I can measure DC offset, though.
 
You need the Dummy load and scope to set the limiters. (And meters?)

The rest is normal DC Balance and Idles.
 
Yeah, that is why I wanted to do a temp fix until I either get the equipment or get someone close to me to adjust that stuff. Is the power supply board the hardest to work on in the Spec 2?
 
Just tested the reed relay on right AWH-045 board. At first both sides of the relay had 0.615 or close reading in resistance mode on my DMM. I tested the relay reed on left AWH-045 and it only had a reading on one side of the relay. Went back to the right side relay and now it only has a reading on one side of about .500 or so. Both relays look like they're original and have been pretty hot, they're a brown color.
 
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I changed the reed relay on the right AWH-048 board and hooked it up to a 100 Watt DBT and the right meter still goes almost wide open and it doesn't come out of protection mode, light stays on.
 
Probably should of mentioned you may have a component issue as well :)
Wait until your order comes in.
Then remove and test the old components and replace with the new.
Check all the diodes and resistors for value and condition.
The resistors sleeved in the fiberglass sleeve should be scrutinized.
Leave nothing for granted. (Except maybe the ceramic and film caps.)
Note:
Most of my repairs on the Spec 2 and 4's involved smoked resistors. Not that I've done a ton of them but you can't overlook the resistors.
 
I thought I found a dead resistor on right AWH-045 R2 resistor.I was testing them in diode mode instead of Ω/resistance mode.
 
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Does anyone have a resistor list they can share? I may order resistors for it since I don't have any that'll work.

Never mind I think all of my resistors are fine.
 
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"It's nice to replace the current limit pots too, but if you do so the amp will have to be re-adjusted. This requires a 4-ohm dummy load capable of a minimum of 200W, a scope, and a signal generator. And someone who can follow the SM instructions." -- EchoWars Link

Sorry to sound dumb, but are the current limit pots VR1 on each AWH-045 boards? If I don't change the current limit pots I won't have to do the 4/8Ω dummy load setting even if I put all new caps, diodes and transistors on the boards?
 
You can figure out what resistors to use based on the values/wattages. Just enter the appropriate information into the parametric search engines. These days, I only use metal film 1% resistors.
As an example, I use these types, for a SX-1010 power supply. the format is what I have setup to generate from my CAD software, for BOM uploading to those distributors.
Digi-key
2,S3.3KCACT-ND,R1,R2
2,S1KCACT-ND,R3,R27
3,S10KCACT-ND,R5,R6,R19
3,S15KCACT-ND,R7,R8,R16
2,S8.2KCACT-ND,R9,R10
3,RNMF12JTD10R0CT-ND,R11,R12,R21
1,1.2KZCT-ND,R13
1,1.5KZCT-ND,R14
1,S18KCACT-ND,R15
1,S30KCACT-ND,R17
1,S330CACT-ND,R18
1,P3.3W-1BK-ND,R20

and these types from Mouser
ERX-1SJ3R3|4
MOS2CT52R122J|1
MOS1/2CT52R100J|3
MFR-25FTE52-30K|1
MFR-25FTE52-15K|1
MFR-25FTE52-330R|1
MFR-25FTE52-10K|1
MF1/4DCT52R82R0F|1
MF0207FTE52-1K8|2
MFR50SFTE52-2K4|1
MFR50SFTE52-2K87|1
MF1/4DCT52R1200F|1
MOS2CT52R152J|1
MFR-25FTE52-18K|1
 
They are an example of what types I used for a SX-1010 I am working on.
If I don't change the current limit pots I won't have to do the 4/8Ω dummy load setting even if I put all new caps, diodes and transistors on the boards?
hard to say if changing that many components will affect the limiter.
 
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