Hello all..
This old beast came to me for general servicing with a low volume and broken volume pot on the right side.
Now, these amplifiers date from mid to late 90's and give a whopping 600w per channel into 4 ohms and 350w at 8 ohms.
If you look at the circuit diagarm there is no latch relay for the speakers but uses a triac crow bar that shorts the output to deck in case of dc fault!.. ie the speakers fries...
Well this had to go and I used my trust fail safe dc protection circuit..much better than blowing up the ampilifer!.
Still after a replacement pot and general clean and dry joints sorted out, she ran clean and powerful.
This old beast came to me for general servicing with a low volume and broken volume pot on the right side.
Now, these amplifiers date from mid to late 90's and give a whopping 600w per channel into 4 ohms and 350w at 8 ohms.
If you look at the circuit diagarm there is no latch relay for the speakers but uses a triac crow bar that shorts the output to deck in case of dc fault!.. ie the speakers fries...
Well this had to go and I used my trust fail safe dc protection circuit..much better than blowing up the ampilifer!.
Still after a replacement pot and general clean and dry joints sorted out, she ran clean and powerful.
Nothing wrong with the crowbar. It has successfully protected loudspeakers for many year and only resets when the power is off.
Better than arcing contacts that do burn out speakers!
Better than arcing contacts that do burn out speakers!
Peavey cs amps use them and over the years I've encountered many a knackered amp due to there triac circuit.. the thing is, yes there simple to add in to save on money for the big company's.
Over the passed 25 odd yrs in servicing I've not seen one welded shut relay..still if you have found a system that works then stick with it.
Over the passed 25 odd yrs in servicing I've not seen one welded shut relay..still if you have found a system that works then stick with it.
trouble is with the crowbar,
9 times out of ten the triac goes short if it gets triggered, blows fuses and (output devices)
this has been my experience over many years with different makes/models
9 times out of ten the triac goes short if it gets triggered, blows fuses and (output devices)
this has been my experience over many years with different makes/models
I have crowbar protection on my home loudspeakers. loudspeakers have worked with about 20 different amplifiers and never did any trouble or faulty trigger.
reading experiences of others,yes I do believe that crowbar protection did some damage on fuses or more if fuses are in front of PSU capacitors, but I also believe that amplifier output got fried first,and that than crowbar did what it supposed to do.
when I did first crowbar protection I have tested it with resistor (actually series of light bulbs for car back light,12V 21W) as load and with another resistor (less than 10r 20W) in series just to protect an amplifier if crowbar triggers wrong. amplifier was able to load about 60V into load resistor. than I changed frequency from 1kHz down to 20 I guess (it was about 10 years ago) and it did not have faulty trigger.
crowbar it self was made by ESP page,I have forgotten what is project number. only critical thing with crowbar is not to use electrolit capacitors, but unipolar film ("dry" capacitors) instead.
in my finally DC protection I will use relay dc-protection only because it has turn on delay and immediately switch off of loudspeakers, and crowbar protection will be between relay dc-protection and loudspeakers. can not be more safe than that.
reading experiences of others,yes I do believe that crowbar protection did some damage on fuses or more if fuses are in front of PSU capacitors, but I also believe that amplifier output got fried first,and that than crowbar did what it supposed to do.
when I did first crowbar protection I have tested it with resistor (actually series of light bulbs for car back light,12V 21W) as load and with another resistor (less than 10r 20W) in series just to protect an amplifier if crowbar triggers wrong. amplifier was able to load about 60V into load resistor. than I changed frequency from 1kHz down to 20 I guess (it was about 10 years ago) and it did not have faulty trigger.
crowbar it self was made by ESP page,I have forgotten what is project number. only critical thing with crowbar is not to use electrolit capacitors, but unipolar film ("dry" capacitors) instead.
in my finally DC protection I will use relay dc-protection only because it has turn on delay and immediately switch off of loudspeakers, and crowbar protection will be between relay dc-protection and loudspeakers. can not be more safe than that.
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Well folks..one more of these amplifiers have arrived with a odd fault.. odd russling sound with just the speakers plugged in and the volume levels at zero..now turning the levels to mid point all is fine??
Well, it will be off with the lid and check things out, and yes, fresh 10k volume controls have been fitted.
More on this later.
Well, it will be off with the lid and check things out, and yes, fresh 10k volume controls have been fitted.
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