Dynacord power mate 1000

[amptech]

dynacord power mate 1000 mk1,

this unit is driving me nut's, polar audio who supply part's for this mixer amp say (1)replacement of the master o/p mixer board should remerdy the fault has they said it's singnal loss before it's reaching the main o/p board!
And a replacement board has been fitted but still the same fault
all o/p transistors have been test ok and there's good clean signal to the left o/p chan, but low o/p to right channel. there's seem's to be that half the signal is being pulled down some were a long the line.

some helpful pointer's would be most greatful on this unit.

many thanks.

[Enzo]

Got a schematic?

[amptech]

Dynacord powermate 1ooomk1

have now got the correct diagram so maybe now can see what is going on here

[amptech]

Dynacord powermate 1ooomk1

Hi all,

Still have same fault with power mate1000mk1.

After replacement of ic 503 lm3080e has informed by polar audio tech's things are still the same what I did notice was limiter led on front mixer panel is on! and when signal tracing on each opamp stage till c2.2uf and the 1k at the long tail pair's that's were singal seem's to dip down low to one side:
now carring out the same trace on the 'good side till the same point the singal is ok.

[amptech]

Dynacord powermate 1ooomk1

Trouble with power mate 1000mk1.

Well some goods news so to speak, o/p was restored via disconecting pin 5 of ic 503 (lm3080e) in the main o/p pcb so good clean signal on both o/p's.
Now, here's the bad news, on the front mixer panel the limter led is staying on. dc offset voltage at both o/p's are +-10 mv's and protection led stay's off as normal. even if pin 5 is reconected the limter led still stay's on with low power on right o/p and normal level on left channel.

has any one had this same fault before?

[Enzo]

SO the 3080 was just doing its job. The limiter circuit decided it needed limiting so it turned on the 3080. Either there is something wrong that is triggering the limiter or the limiter circuit has a failure. If you cold post the schematic, we'd be more able to help.

[amptech]

Dynacord powermate 1ooomk1

At long last! all is well and now this pain in the butt unit is working as it should be

The fault lay with in the limiter circuit a 220k ref point r542 was o/c that feeds from the 15 volt+ line and a compare check using the good channel soon showed up different voltage readings.

well it just goes to show 'keep at it and with a bit of luck,time and checking your reach your goal

Enzo, what is your email address so that I can send over the diagrams on this unit.

[Enzo]

If they are less than 1 MB you can post them right in the thread. Otherwise, drop me an email through my user profile, and I will respond. I don;t put my email in threads anymore - when I do, I will get a steady stream of them forever. I mentioned a MArshall schematic over in DIYAudio.com forum once like 7 years ago and I still get a request for it once a week from that.

I may even have to turn off my email here soon, due to volume.