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.

Yamaha P4500
Yamaha P4500
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
Thread Tools Search this Thread
Old 5th December 2012, 06:31 PM   #11
toprepairman is offline toprepairman  United Kingdom
diyAudio Member
Join Date: Nov 2010
Hi Tarzan.
Yes agreed the caps are 160V, but given that manufacture provides for 100 or 160V then that's what they need to be.
I've taken a further look at the unit and have since decided that 140V is probably correct, the 24V olt rails are about right.
The problem is the PNP output devices keep failing and I suspect it's due to exceeding the Vce max of the devices. The ramp up waveform from the EEEngine looks correct when compared to the other channel.
If run at reduced mains Volts then all is well. if the supply is taken to full mains then all still Ok. But if the input signal is taken up to max with the output swinging rail to rail then another PNP device shorts out (due as far as I can see to excess Vce).
I have 56R resistors in the rails to limit current so don't get catastrophic failure and running into a 100R load.
Any ideas?
  Reply With Quote
Old 5th December 2012, 06:49 PM   #12
toprepairman is offline toprepairman  United Kingdom
diyAudio Member
Join Date: Nov 2010
Looking at the specs, it only claims 460 Watts into 8 Ohms. I'm assuming that's RMS, though it doesn't actually say so.
Doing the maths the peak output volts is 86 volts. lets say we lose 10 Volts across the devices (it should be less then that) so thats 96 volt rails.
The transformer is very big so regulation should be in the 5% regeion but even if we allow 10%, then our unloaded rail doesn't need to be above 110 Volts. Ok be generous and a high mains voltage and we're looking at a max of 120 Volts. Hence my suspition of the measured 140 Volts.
  Reply With Quote
Old 6th December 2012, 06:16 PM   #13
Tarzan is offline Tarzan  Belgium
diyAudio Member
Tarzan's Avatar
Join Date: May 2004
Location: Genk
are you in need of the service manual?
There is not much in it but it can help with the biasing.
If the pnp's are failing all the time; then there must be another problem with the drivers probably?
I doubt very much that Yamaha will deliver an amp with a problematic final stage.
And the other channel is working fine?
Must be someting else...
  Reply With Quote
Old 7th December 2012, 07:44 AM   #14
toprepairman is offline toprepairman  United Kingdom
diyAudio Member
Join Date: Nov 2010
A service manual would help possibly, I only have a copy of the circuit.
Agreed these amps have a very good reputaion for reliability and there's no way Yamaha could have got away with selling so many of them if there was any question there.
No there's definitly a fault but it's hiding itself well.
The other channel is fine, and the owner has had this unit from new.
It just died on one channel and he continued to use the other channel with no problems.
  Reply With Quote


Yamaha P4500Hide 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
Yamaha AX-390 Predator864 Solid State 15 15th July 2011 08:36 PM
yamaha P4500 east electronics Solid State 3 3rd February 2009 08:30 PM
Teac CD-P4500 paolofina Digital Source 2 17th October 2008 02:26 PM
Yamaha A-550 angel Solid State 4 18th January 2006 01:22 AM
Yamaha Amp Dynsdale Solid State 5 29th September 2005 07:32 PM

New To Site? Need Help?

All times are GMT. The time now is 01:39 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio