Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th August 2012, 06:15 AM   #31
svs88 is offline svs88  Finland
diyAudio Member
 
Join Date: Jul 2012
Location: Pori
Quote:
Originally Posted by jitter View Post
A warning here: don't put the amp on standby with the protection module removed! The high voltage on Q315 may lead to damage if you put the amp on standby. The circuit around Q315 was designed for approx, 5 V, not nearly 10 times more.
Ok, already did :/. No smoke or anything odd happened, need to check the circuit when i get home.

Ill try to solder joints of module later today and try it again. New UPC1237 should arrive in couple of days so i might try to mod circuit for it. I think ill also need 56k resistor between pins 8 and 7 also for it.
  Reply With Quote
Old 15th August 2012, 03:04 PM   #32
Bill_P is offline Bill_P  United States
diyAudio Member
 
Join Date: Sep 2009
Location: New York, the vampire state
The C315BEE service manual has a conflict between the schematic and parts list. The schematic shows the circuit board module you found in the amplifier. The parts list incorrectly lists UPC1237 and as you noted several modifications would be needed to use the UPC1237 in circuit.

There are a number of components that need to be changed to use the UPC1237 and in some cases the component value must be calculated based on the voltages in the C315BEE. To do this right will require a fair amount of work and testing to be sure it was done correctly.

The module is just a discrete circuit with transistors and diodes that should be easy to repair. That would be the much preferred path in my opinion. The NAD C352 and C372 revised service manuals have a schematic for the protection module. It is probably the same module that is in your 315BEE. The schematic will be helpful in repairing the module if you decide to go that route.

You can get the service manuals at ElektroTanya | Service manuals and repair tips for electronics experts. There are several listing for each amplifier. For the C372 choose the entry NAD C-372 SM 2; for the C352 choose NAD C-352 SM.
  Reply With Quote
Old 15th August 2012, 05:11 PM   #33
svs88 is offline svs88  Finland
diyAudio Member
 
Join Date: Jul 2012
Location: Pori
Quote:
Originally Posted by Bill_P View Post
The C315BEE service manual has a conflict between the schematic and parts list. The schematic shows the circuit board module you found in the amplifier. The parts list incorrectly lists UPC1237 and as you noted several modifications would be needed to use the UPC1237 in circuit.

There are a number of components that need to be changed to use the UPC1237 and in some cases the component value must be calculated based on the voltages in the C315BEE. To do this right will require a fair amount of work and testing to be sure it was done correctly.

The module is just a discrete circuit with transistors and diodes that should be easy to repair. That would be the much preferred path in my opinion. The NAD C352 and C372 revised service manuals have a schematic for the protection module. It is probably the same module that is in your 315BEE. The schematic will be helpful in repairing the module if you decide to go that route.

You can get the service manuals at ElektroTanya | Service manuals and repair tips for electronics experts. There are several listing for each amplifier. For the C372 choose the entry NAD C-372 SM 2; for the C352 choose NAD C-352 SM.
Thanks for replying.

I downloaded the C352 and c372 service manuals, and it seems they have separate upc1237ha ic (opamp symbol at schematics) so not the same as pictures in my earlier posts. Atleast i think so. You can see it right, under the green led (8 pin ic).

Click the image to open in full size.
  Reply With Quote
Old 15th August 2012, 05:42 PM   #34
Bill_P is offline Bill_P  United States
diyAudio Member
 
Join Date: Sep 2009
Location: New York, the vampire state
If you got the right manuals, the protection module schematic is on page 18 for C352 and page 21 for C372. There is also a description of what components changed from the original UPC1237 circuit. The C352 and C372 were transitional models in which early production used the UPC1237 and later units used the replacement module.

The first page of the C372 manual should be dated November 2006; the C352 manual is January 2007.

Last edited by Bill_P; 15th August 2012 at 05:44 PM.
  Reply With Quote
Old 15th August 2012, 05:53 PM   #35
svs88 is offline svs88  Finland
diyAudio Member
 
Join Date: Jul 2012
Location: Pori
My manuals are too old, both are May 2005. Downloaded from the link.

EDIT: Found it! Cheers mate!

Last edited by svs88; 15th August 2012 at 06:22 PM.
  Reply With Quote
Old 18th August 2012, 05:41 AM   #36
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
I had a look at the modifications in the service manual of the C372SM2 needed for replacing the UPC1237 with the module and I'm pretty sure it's the same for your amp.

It looks like the only modifications you'll need to do to be able to use the original UPC1237 instead of the replacement module are:
- reverse the polarity on D303;
- remove C335 and replace with 4.7uF/50 V, mount new cap reversed polarity;
- insert a 47k or 56k resistor between pin 7 and 8 of the IC (the parts list in manual of the C372SM2 lists R777 as 56k, but the modification instructions say it's 47k, either will probably work fine).

Good luck and let us know if you're successful!

Last edited by jitter; 18th August 2012 at 05:55 AM.
  Reply With Quote
Old 18th August 2012, 06:43 AM   #37
svs88 is offline svs88  Finland
diyAudio Member
 
Join Date: Jul 2012
Location: Pori
Protection module itself is so small that i thought it would be easier doing the mods for UPC1237. IC is still on the way, i expected that it would arrive yesterday but it seems it goes over the weekend.

Thanks for listing the instructions, resistor was a question mark for me.

This "case" was my first time on the forums, and its really nice to see so many helping hands here. I'll let you how this project ends
  Reply With Quote
Old 18th August 2012, 06:53 AM   #38
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
As an aside:
Looking back at post #28, I realize that the C315BEE must have been designed to take the replacement module from the start, despite its parts list listing the UPC1237 as the protection module.
Added to the absence of modification instructions in the service manual, the absence of traces and mounting holes in the pcb trace-layout for a resistor between pin 7 and 8 is a big giveaway. Same goes for polarity of D303 and polarity and value of C335 in schematics.

But I wonder why NAD didn't design the amp with another off the shelf protection IC in the first place... I can't help but think that manufacturing a discrete replacement module is far more expensive than using an alternative IC.
Perhaps NAD designers didn't pay enough attention to obsolescence warnings from the IC manufacturer and went ahead making new designs using it anyway. The status of a component changing from "Active" to "NRND" (not recommended for new design) is usually the first sign that a manufacturer is going to stop production.
  Reply With Quote
Old 25th August 2012, 02:29 PM   #39
svs88 is offline svs88  Finland
diyAudio Member
 
Join Date: Jul 2012
Location: Pori
Its alive! Got the upc1237 ic at thursday and i installed it with the mods yesterday. Saddly i didnt have 4,7 uF 50V capacitor, so installed 10 uF 60V instead. It seems that cap size affects the time what it takes to pull the relay, with 10 uF it is around 2 seconds. Fast enough to me.

Another problem was found that only left speaker was working. Found that the lead from relay output to speker connector was open. Soldered lead again and got it working. Maybe that was the reason for broken protection circuit?

Anyway, thanks to everyone who helped, especially jitter and Bill_P
  Reply With Quote
Old 26th August 2012, 06:53 AM   #40
jitter is offline jitter  Netherlands
diyAudio Member
 
jitter's Avatar
 
Join Date: Aug 2004
Location: Eindhoven, The Netherlands
Quote:
Originally Posted by svs88 View Post
Its alive! Got the upc1237 ic at thursday and i installed it with the mods yesterday. Saddly i didnt have 4,7 uF 50V capacitor, so installed 10 uF 60V instead. It seems that cap size affects the time what it takes to pull the relay, with 10 uF it is around 2 seconds. Fast enough to me.
Good to know that you fixed your amp!

The longer time for the relay to switch on with the 10 uF cap is to be expected as it takes longer for the voltage to reach the threshold than with the 4u7 cap (for the same reason as I explained in post #24).

If you don't mind one more replacement, then you could replace R320 with a 10k resistor. This should shorten the delay and would be closer to the recommended optimum value in the datasheet of the UPC1237 (see fig. 5 on page 6, with ~17 VAC, the optimum value is 10k, and the C372SM2 indeed uses 10k for R787).
But this value isn't very critical, if you don't mind the slightly longer delay at power up, then you can leave your amp as it is now just fine.

Quote:
Another problem was found that only left speaker was working. Found that the lead from relay output to speker connector was open. Soldered lead again and got it working. Maybe that was the reason for broken protection circuit?
Not likely, the protection circuit only drives the actuating coil of the relay. Wether or not the audio signal reaches the speakers, doesn't matter to the protection circuit.

Quote:
Anyway, thanks to everyone who helped, especially jitter and Bill_P
You're welcome!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Nad T752 Repair - help! audio_tony Solid State 16 9th September 2012 12:54 AM
Nad Receiver Repair bwz123 Introductions 2 11th October 2011 10:43 PM
NAD C542 Repair -- Help! robber222 Digital Source 0 24th October 2010 09:14 PM
nad c315bee nosound output uplees Solid State 0 31st March 2010 03:06 PM
NAD 3150 repair nukaidee Solid State 4 1st September 2009 04:07 PM


New To Site? Need Help?

All times are GMT. The time now is 08:45 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2