Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Challenged myself restoring a Pioneer A-333. What dirty thing!
Challenged myself restoring a Pioneer A-333. What dirty thing!
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 September 2019, 01:53 PM   #1
StewartH83 is offline StewartH83  England
diyAudio Member
 
Join Date: Jan 2019
Location: Stockport, Greater Manchester
Send a message via MSN to StewartH83
Default Challenged myself restoring a Pioneer A-333. What dirty thing!

So I paid £30 odd for this A-333 to restore and can't believe how thilfy it was. After a dry brush down I cleaned it with bicarbonate of soda mixed with distilled water. Now looks great.

I noticed two resistors were burnt out which I've replaced. I wanted to know what you think would of caused it? It's on the phono input.

I've recapped it now and really transformed the sound. Especially the power amp stage with new Panasonic/Nichicon caps and main filter caps well improved the bass.
Attached Images
File Type: jpg IMG_20190913_113657.jpg (833.4 KB, 230 views)
File Type: jpg IMG_20190913_113708.jpg (980.0 KB, 228 views)
File Type: jpg IMG_20190914_182053.jpg (848.9 KB, 220 views)
  Reply With Quote
Old 20th September 2019, 01:59 PM   #2
StewartH83 is offline StewartH83  England
diyAudio Member
 
Join Date: Jan 2019
Location: Stockport, Greater Manchester
Send a message via MSN to StewartH83
Also I want to replace these 4 resistors and want to make sure they are 4.7 ohms? It's hard to tell if the coloured strip is blue or violet. With the schematics having an exclamation mark inside the triangle I have to get it correct.

Much appreciate any input
Attached Images
File Type: jpg IMG_20190914_181843.jpg (763.0 KB, 215 views)
File Type: jpg Screenshot_20190919_171625_com.google.android.apps.docs.jpg (529.6 KB, 213 views)
  Reply With Quote
Old 20th September 2019, 02:50 PM   #3
MarsBravo is offline MarsBravo  Netherlands
diyAudio Member
 
MarsBravo's Avatar
 
Join Date: Feb 2017
Location: NL
4E7 is a standard E12 value, 4E8 would be very curious. Drawing indicates 4E7 too.


Dirty it is!
(Cough)
__________________
Y/Yo=(1-X/Xo)exp2 <> Y/Yo=(e)exp(X/Xo){Xo=kT/q}
  Reply With Quote
Old 20th September 2019, 03:16 PM   #4
StewartH83 is offline StewartH83  England
diyAudio Member
 
Join Date: Jan 2019
Location: Stockport, Greater Manchester
Send a message via MSN to StewartH83
Haha it stinked. First time I cleaned boards thoroughly by wetting it with distilled water mixed and drying with a heat gun. I forgot to picture it after doing that and recap but well impressed with the process it don't smell now.

Really made me appreciate the audio engineers out there as its a pain to pull apart. Luckily a section of bottom panel comes off to reach those 4 resistors

I'll go with 4.7s, they look like they been through some stress

Thank you MarsBravo!
  Reply With Quote
Old 20th September 2019, 03:42 PM   #5
MarsBravo is offline MarsBravo  Netherlands
diyAudio Member
 
MarsBravo's Avatar
 
Join Date: Feb 2017
Location: NL
Take 1W power rating for these R's or 2W if fitting, but no wirewound anyhow!


Do you have two watt resistors?
For what?
No two?
To what?
Yes!
?
__________________
Y/Yo=(1-X/Xo)exp2 <> Y/Yo=(e)exp(X/Xo){Xo=kT/q}
  Reply With Quote
Old 20th September 2019, 04:02 PM   #6
StewartH83 is offline StewartH83  England
diyAudio Member
 
Join Date: Jan 2019
Location: Stockport, Greater Manchester
Send a message via MSN to StewartH83
Hahaha your funny!

I have no 1 or 2 watt in that value. Yet was going to order 1 watt types. I'll check RS components for their 2 watt ones. The schematic says 1/4 or 1/2 watt unless stated. They are slightly smaller than the 1/2 watt resistors I have.

Do carbon or metal film handle heat better?

Well appreciate your suggestions sir
  Reply With Quote
Old 20th September 2019, 06:56 PM   #7
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
The exclamation mark on the resistors likely means they are "fusible" resistors.. ie designed to blow open circuit when overloaded.
  Reply With Quote
Old 20th September 2019, 07:53 PM   #8
sgrossklass is offline sgrossklass  Germany
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
Quote:
Originally Posted by jaycee View Post
The exclamation mark on the resistors likely means they are "fusible" resistors.. ie designed to blow open circuit when overloaded.
They will occasionally do so when not overloaded as well. Some amps are downright notorious for bad fusible resistors.

The burnt resistor next to CN17 would appear to be R299. That's a 10 ohm resistor connecting power amp input ground to chassis ground. Under no normal circumstances would this have any reason to blow up like it did, at least I fail to see any failure mode that would do this. (Service manual is on HiFiEngine.) Measure voltage across it, and if nothing substantial is found, replace the part and see what happens.


The 4.7 ohm resistors (R265 et.al.) are given as part no. RFA¼PS4R7J, so quarter watt 4.7 ohm 5% tolerance.

Last edited by sgrossklass; 20th September 2019 at 08:14 PM.
  Reply With Quote
Old 20th September 2019, 08:43 PM   #9
StewartH83 is offline StewartH83  England
diyAudio Member
 
Join Date: Jan 2019
Location: Stockport, Greater Manchester
Send a message via MSN to StewartH83
Fantastic inputs guys.

The exclamation mark is in a triangle on the schematics but don't see any on accual resistor, apologies if I caused confusion but really good to know for the future, interesting.

Yeah R299 was replaced with a 10 ohm half watt, I'm surprised it worked previously while burnt.

I have the schematic from hifi engine. God send that site and a couple of others. Still unable to find service manual for the Denon PMA250 (Mark III) I've been working on though, need to set the bias.
  Reply With Quote
Old 20th September 2019, 08:45 PM   #10
StewartH83 is offline StewartH83  England
diyAudio Member
 
Join Date: Jan 2019
Location: Stockport, Greater Manchester
Send a message via MSN to StewartH83
Here's it cleaned up with resistors and some caps changed.

Theres no pots, does the ICs set the idle current?
Attached Images
File Type: jpg IMG_20190920_181653.jpg (880.2 KB, 112 views)
  Reply With Quote

Reply


Challenged myself restoring a Pioneer A-333. What dirty thing!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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Pioneer A-616 worth restoring? Tex Houston Solid State 4 2nd March 2016 11:27 AM
Mathematically challenged help for lm 317-337 semi932 Power Supplies 18 5th January 2011 10:16 AM
Restoring a Pioneer QA-800A quadra flambart Solid State 11 9th December 2010 04:23 AM
Help please for opamp challenged.......... rabbitz Solid State 3 6th April 2004 02:42 PM


New To Site? Need Help?

All times are GMT. The time now is 06:51 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki