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NAD 317 Protect problem

S

StickWeapon

New Member
Hi guys! I have problem with this amp. I have found damaged elements on psu board - diode d210, q202 (2sc1815) i have changed q201 (2sd600), q204 (2sb631) because those can be very hot, q203 (2sa970), amp is after recap now but still in protect mode. Left channel is working correctly, You can change idle current but right channel on test points 1.5mv. After remove power transistors from right channel prptection went out. I bought new transistors but protection with new transistors come back.
 
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Hello, I own a NAD 317 bought new in 1999, it has boards dated 1995 so now 30 years old. I had a number of problems, starting with the Mute relay causing static, and other preamp input relays causing low level distortion, replaced them but more serious problems occurred months later, like on startup booming static in Left channel with no source and Volume at minimum, protection was also coming on, then when checking on bench noticed heat sinks started getting real hot with no load. Several people, here and elsewhere, kept telling me I was wasting my time trying to fix it. I finally agreed with them and bought a new integrated amp, glad I did!

Idle current should be 20 mV, I remember having difficulty getting the Left channel idle current set, I would set it, but after more booming static went back and found it was out of spec again.

That is the best advice I can offer. Now I did run it with 4 ohm speakers the whole time I owned it, without realizing it was never rated for continuous 4 ohm loads. That made it run hot, so always had a pancake fan on top to keep it cool, that likely extended the lifespan. My new amp does have a continuous 4 ohm rating.

What is the ohm rating for your speakers?
 
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Left channel is perfect (20mv) on right channel I can't adjust always 1.5mv. It's not mine amplifier I'm only repair that. I think something is with te right channel board because without power transistors on right channel protect gone. On left channel 2 diodes have 52v but on right one diode have 1.5v and second 102v. Voltage coming to boards is correctly for both channels (52v).
 
Try contacting RTally, go to Members and search by name, he has a 317 and is more experienced than I am. He helped me diagnose a problem with my 317.
 
You may have better luck asking a moderator to move this thread to the Solid State sub-forum. Click the Report link and ask a Mod to move the thread. I am but a neophyte at repairs compared to others that frequent the Solid State sub-forum.

In summary, your left channel is working fine, but your right channel is not.

on right one diode have 1.5v and second 102v.
Click to expand...
Did you measure this with or without the output transistors in circuit?

What diodes are you referring to? The right amp board shows four diodes: D302 and D306 on positive side and D304 and D308 on negative side.

Are you using a dim bulb tester?
 
Measure with transistors. On right channel D308 and D306 (1n5402). On left channel is D305 and D307. Only using multimeter. Thank You for reply.
 
Imeasure all transistors on right channel, one looking suspect, i try to solder transistors from right to left channel and from left to right to see if right channel start working but it is worse. Now after replacement fuse 4a is burning, all is soldered good i checked 10 times...
 
I suggest using schematic reference numbers when referring to components. The parts list shows four fuses, none of them are 4 amp. If you do not have the service manual, it is easily found via Google.

Sounds like you have some failed transistors. I do not know your knowledge level, but these two links offer great info on testing your transistors.
Bipolar Junction Transistor Testing Basics
Testing Transistors

The first order of business is to test to see which components have failed.

Do not power up the receiver without using a dim bulb tester. Do not swap components to see if it works. Doing that is likely to burn out good components.

I suggest removing the output transistors and testing them. If you find failed transistors, test the transistors upstream. Let us know what you find, specifically.
 
End power transistors was checked and was good with diode test. Anyway I replace them with new one and the same result... all output transistors were fine with diode test. I replace them with new one
 
The fact that you are blowing the power supply main fuse indicates that there is a high current short. That is why using a dim bulb tester (DBT) is important. You never answered, are you powering the unit with a DBT? I am assuming you are not.

You said that for D306 and D306, you measured 102 V across one and 1.5V across the other (but you did not say which diode). This indicates that one of the rails has a very low impedance short to the common O/P, thereby giving a dc offset to the common and triggering the protection circuit. Normally, such a condition indicates that the output transistors have a collector-emitter short. It may also indicate that the one or more of the driver transistors have a collector-emitter short, which is driving the associated output transistor to full conduction.

StickWeapon said:
End power transistors was checked and was good with diode test. Anyway I replace them with new one and the same result... all output transistors were fine with diode test. I replace them with new one
Click to expand...
Did you test the transistors (Q322, Q326, Q324, Q328) upstream?

How are you doing the diode test? A DMM? A tester? It would be helpful if you provide more details of the steps you are taking.
 
Yes, all transistors was tested in diode test. All was fine, i think lile You and changed all driving and ppwer transistors. After replace nothing happened new, the same idle current was 1.5mv for right channel. After test all transistors (all in diode test) are correct. Replace them with left channel and from now main fuse is burning so someone transisotr must be damaged (with power). D306 has 102v and D308 has 1.5v
 
What is the provenance of your 317? Was it functioning normal and then failed? Did you get it in a failed condition? Or did it fail after you started working on it?

How are you measuring voltages if the PS fuse keeps popping?

I am having trouble following what you are doing. Please provide the conditions under which you are testing and the results. Are you testing transistors in circuit or out of circuit? What configuration is the 317 in when you measure the diode volages? Output transistor in or out? Fuse blown? on DBT?

Your first post said you recapped the amp. Did you replace all caps in the amp? Was the amp working before you did a recap? Have you gone back and verified your work: correct size, polarity, and placement of every cap; all solder connections are good; etc.
 
Aplifier was in protect before repair. Owner bought in this condition. I found many dry capacitors with high esr so we decide to recap and repair protect. I measure transistors unsoldered from pcb. PSU board was checked all elements unsoldered and found damaged elements like diode d211 (short circuit), q202 (2sa1815). Rest of components are good. Protect only vanished when remove power end transistors (from right channel) so faulty must be in right channel block. Now output transistors are in (new) with new drivers. I verified my work 5 times. I made all solder points fresh. All voltages to left and right channel are perfect, only diode d306 has 102v and d308 only 1.5v. On left channel was correct D305 and D307 exactly 52.5v. Now i unsolder all transistors from right and left channel to measure them and replace them in right and left channel with hope right channel start working and left stop. After that operation fuse starts to popping.
 
On base and emitter of c3519 and a1386 is 44v, on collector is fine 52v. On working channel (left) is 0.6mv on base and emitter. Must be something wrong on psu board. Every element has measured and changed on right channel board.
 
I've been reading through this thread. PSU is common for both power amp stages.
Are you certain the 1N5402 didoes in the right channel are wired correctly? These diodes, if connected correctly, should be in reverse bias condition with the
+55V and -55V connections (hence: should not be conducting current flow).
 
If you are correct in all the components being good then there's a wiring issue.
Since you seem to have a good left channel have you done ohmic test point measurements comparing left to right channel measurements (of course no power applied)?

Example test left channel connection (anode D305 to +55V connection then anode D305 to -55V connection then on right channel anode D306 to +55V / -55V connections).
 
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