Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 436
Default Yamaha dsp-z7 doa


The ac line relay cycles for 500mS, without display indications.
This with or without main TX connected.
Housekeeper is live and rises to 13V during the start-up
attempt. Power detect line ok.

Anyone familiar with start-up sequence of this thing?

Looks like you've got to disassemble the whole thing to get
at the processor/control area.

Is it safe to bypass relay, to run up the power gradually?

RL
  #3   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 436
Default Yamaha dsp-z7 doa

On Tue, 2 Jun 2020 18:28:17 -0400, M Philbrook
wrote:

In article ,
says...

The ac line relay cycles for 500mS, without display indications.
This with or without main TX connected.
Housekeeper is live and rises to 13V during the start-up
attempt. Power detect line ok.

Anyone familiar with start-up sequence of this thing?

Looks like you've got to disassemble the whole thing to get
at the processor/control area.

Is it safe to bypass relay, to run up the power gradually?

RL


I have no idea basically what you are talking about except maybe a power
management circuit that isn't getting a watch dog trigger from the CPU ?

Normally those kinds of circuits requie some sort of feed back
information to keep it alive...

I Suppose the proper thing to do is watch that feed back information to
see if this is the case.

In some cases it could be a rather high speed pulse coming from a
Digital timer or CPU. when that stops the circuit will time out and shut
down..

I assume this is what you are referring to ?


Even with a full schematic, the requirements for the main processor
to keep the line relay closed and running is not obvious.

Two of these cycles from O/I switch latches the unit off until
line input power itself is cycled.(There is a dual flipflop in the
housekeeping circuitry).

All supply lines are monitored to develop 'power good', but there's
no obvious power circuit failure evident during the period of relay
closure - except that the front panel doesn't even blink.

All service troubleshooting involves interaction with the front panel
display. . . .with specialized harness extenders and board
substitutions.

The harnessing is nuts, with signals routed through 4 or 5 cards and
connectors before arriving at their destination. I expect the
organization of power circuits and control logic will be similarly
convoluted.

I've told the owner - no repair / no charge - take it to Yamaha
service - but it hasn't been picked up since.

RL
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Yamaha receiver has slight noise/static only in DSP modes. Ideas on where to look? tem00 Electronics Repair 2 November 29th 06 10:01 AM
Yamaha DSP A-990 steve Electronics Repair 3 November 7th 06 12:41 PM
Yamaha DSP Amp has hum and low sound on one channel ElectroNovice Electronics Repair 6 February 4th 06 12:50 AM
Yamaha DSP-A492 Peter Ibberson Electronics Repair 0 February 22nd 05 11:33 PM
Anyone have a schematic for a Yamaha DSP-A780? Kai Robinson Electronics Repair 2 December 18th 03 06:03 AM


All times are GMT +1. The time now is 09:13 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"