Grounding dedicated PSU for SAA7220 - Page 7 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

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 20th November 2011, 11:49 PM   #61
diyAudio Member
 
Join Date: Jun 2008
Excuse me if this is me being a bit simple but... a short on pin 16 and 17 when it was switched on ?
Do you think you really did that ?
  Reply With Quote
Old 20th November 2011, 11:54 PM   #62
diyAudio Member
 
Join Date: Jun 2008
...sorry....maybe a solder blob or something did it ?

I fried an ' A ' with that error once - it's something you don't forget.
I now have a magnifying lense to check all important connections to make sure there are no shorts before I switch anything on now.

Fingers crossed it's something simple that you'll spot and rectify - and not a fried chip.

Good luck

Andrew
  Reply With Quote
Old 21st November 2011, 06:10 AM   #63
josha is offline josha  United Kingdom
diyAudio Member
 
Join Date: Apr 2005
Location: Holmfirth, West Yorkshire
I built the mod under the chip so I had quite a lot going on around those pins, I do check my work though - it's the only thing I can think of (yet) that could have upset it, for once I hadn't tweaked anything else at the same time!

I'll double check everything before writing it off!

Thanks, Josh.
  Reply With Quote
Old 21st November 2011, 08:50 AM   #64
simonov is offline simonov  Bulgaria
diyAudio Member
 
simonov's Avatar
 
Join Date: Aug 2005
Location: PZ
Remove the TDA1541 chip and check the power supply ratings. If you have a scope check the signals from the digital filter.
  Reply With Quote
Old 21st November 2011, 08:39 PM   #65
josha is offline josha  United Kingdom
diyAudio Member
 
Join Date: Apr 2005
Location: Holmfirth, West Yorkshire
Hi, voltages all look ok, -5v on p26, +5v on p28 and -15v on p15. Waves all look ok as well I think (see attached - filename denotes the pin). To be honest, I'm not entirely sure what I'm looking at here but everything seems present and correct(!).

Out of interest I popped the original non-a in for a test after checking all the voltages and I get no sound at all! This could be a result of me chopping and re-clocking everything though (I'm guessing).

I'm away for a couple of days this week but I'll do some more digging on my return - I'm not giving up on this yet - it sounded fantastic just before it died and I'd love to find out what I've done

Again, thanks for all your help with this, I'd still be putting up with mediocre sound if it wasn't for this forum!
Attached Images
File Type: jpg pin1.JPG (242.4 KB, 132 views)
File Type: jpg pin2.JPG (239.1 KB, 132 views)
File Type: jpg pin3.JPG (238.6 KB, 126 views)
File Type: jpg pin4.JPG (240.7 KB, 123 views)
  Reply With Quote
Old 26th November 2011, 10:03 AM   #66
josha is offline josha  United Kingdom
diyAudio Member
 
Join Date: Apr 2005
Location: Holmfirth, West Yorkshire
Hi all,

After some more poking around with the scope it seems the signal present on pin3 above is constant, ie doesn't change when the CDP is 'playing'. However the data out (pin37 on the 7210) does, ie it jumps to the 'eye' pattern when you press play. hmmm - this leads me to think the problem lies in 7220, it's outputting a signal on the data line whether the CDP's playing or not.

Further investigation required!
  Reply With Quote
Old 26th November 2011, 10:50 AM   #67
simonov is offline simonov  Bulgaria
diyAudio Member
 
simonov's Avatar
 
Join Date: Aug 2005
Location: PZ
I have no scope at home to test my player. The simple logic shows that some of the internal blocks of the 7220 chip might be dead.
  Reply With Quote
Old 27th November 2011, 09:11 PM   #68
josha is offline josha  United Kingdom
diyAudio Member
 
Join Date: Apr 2005
Location: Holmfirth, West Yorkshire
Well - there we go, by messing around with something unrelated I managed to upset the SAA7220, who'd have thought it?

So....good opportunity to try NOS (no choice really, I haven't got a spare 7220!), it is very dead and won't even mute so I get a jump when playing the first tracks but I can live with that until I figure something out, it plays ok otherwise. (The 7220 is essentially out of the circuit now).

I also had a very distorted sound until I realised that the bit clock was still running at OS speed(!), it's now running at /4 and seems happy enough.

Too early to tell (and too long since I last heard the player) to decide if I prefer NOS, all I know is the player sounds very detailed and refined, there's not quite as much gain as I'd like from the output stage but apart from that - very happy!!!

ahh - I just found out the pause just makes it jump, no mute might get annoying after all!

Last edited by josha; 27th November 2011 at 09:15 PM. Reason: Addition!
  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
Dedicated PSU for DEQ/DCX2496 stef1777 Power Supplies 337 19th December 2011 10:58 PM
Star grounding with dedicated pathes bobodioulasso Solid State 1 11th June 2010 05:58 PM
Separate PSU grounding decky Power Supplies 1 20th March 2008 09:40 PM
Saa7220 sparks from ground pin (killed a saa7220 ?) ash_dac Digital Source 26 26th March 2006 03:32 PM
LM3875 kit grounding, optimal grounding for separate amps and psu? findog Chip Amps 9 16th May 2005 10:27 PM


New To Site? Need Help?

All times are GMT. The time now is 10:24 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