Martex M200 amps

no I pulled the amp and DLT off ,I checked the AC right out of the variac. I deoxit the variac and now the scale is only 5v off it was real dirty . full out put no load 143vAC . What do you think , bring up the amp on just the variac ?
 
All is good ,I went 120vAC which give +&- 58vDC the boards are rated for 10vDC to 70vDC . I'll pass a signal through tomorrow I'm curious on how the meters will work not mention the amp . thanks
 
I pass a 1kHz signal @ 0.5v and the VU meter was at-6db the lower VU was at 50 watts. ( this test only tells me that it works ?) This was done with no dummy load. VU's dial scales are -20db to +3db, the lower scale is 0 to 100 an 100 is at 0db. I think my next step is to mount the board on the heat sinks and test it with a load and see what output I'm getting from the input .
 
Yeah, sounds like you need to adjust the resistor on the meters. Be careful coming up on a load and watch those meters, don't want to over excursion them critters.
 
Do you think I can use the meter adjustment procedure for the Pioneer spec-4 on this amp ? procedure as follows ...apply 1kHz to input and adjust input so voltmeter on speaker terminals read 34.64v adjust meter to 0db. I think I have to put AC meter on the speaker terminals to get some idea of the gain of this amp.
 
I think the problem with this side may have been the power supply's "crowbar circuit" ( has no zener diode) . But I'm still testing it. I want to use the mono boards I bought from China in these amps when there stable.
I also I have a speaker protection board I would like to install that requirers 12-18VAC (15VAC suggested ) .Can I get the 15VAC from the primary of one the transformers ? The VU lamps get there voltage from the primary also. What do you think ? is this enough info to answer my questions ? thanks
 
calman46 said:
Do you think I can use the meter adjustment procedure for the Pioneer spec-4 on this amp ? procedure as follows ...apply 1kHz to input and adjust input so voltmeter on speaker terminals read 34.64v adjust meter to 0db. I think I have to put AC meter on the speaker terminals to get some idea of the gain of this amp.
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You want the rated outputt to show 0db, measure the output in AC and go from there.
 
calman46 said:
I think the problem with this side may have been the power supply's "crowbar circuit" ( has no zener diode) . But I'm still testing it. I want to use the mono boards I bought from China in these amps when there stable.
I also I have a speaker protection board I would like to install that requirers 12-18VAC (15VAC suggested ) .Can I get the 15VAC from the primary of one the transformers ? The VU lamps get there voltage from the primary also. What do you think ? is this enough info to answer my questions ? thanks
Click to expand...

If there's a 15 volt winding, yeah use it.
 
No 15v winding. I want to "steal" 15vac from somewhere . The VU meter lamps are powered from the primary winding with some resistors .What about taking the voltage from there with some resistors to get the 15vac? I have check to see what voltage the lamps are using.Doesn't Don power is speaker relay kit for the PL400 something like this?
 
Straight off the secondary windings but the relay coil voltage is 48vdc. Got a schematic for the DC protect?
 
No schematic just a connection diagram. I have 25VAC on the lamps. I never seen lamps wired this way before. One winding lead is on the + side of one lamp and other winding lead is on the - side of the other lamp and there is wire with a diode and a resistor between the other two lamp terminals.Do you think I could get the15v here some how?
 
Google "Voltage dividers" or "Zener regulated voltage"....
 
calman46 said:
I think the problem with this side may have been the power supply's "crowbar circuit" ( has no zener diode) . But I'm still testing it. I want to use the mono boards I bought from China in these amps when there stable.
I also I have a speaker protection board I would like to install that requirers 12-18VAC (15VAC suggested ) .Can I get the 15VAC from the primary of one the transformers ? The VU lamps get there voltage from the primary also. What do you think ? is this enough info to answer my questions ? thanks
Click to expand...

Use a small form factor AC wall wart transformer.
 
I like both ideas . I could power the wall wart of the amps power cord in side the chassis ,it would be like adding and AC outlet . I have to test(push it some) the amp and see if its stable . Stay tuned .................
 
I played some music through the problem side using the original amp board and it sounded good. But this board has seen better days, with how many times it has been worked on. Just to clarify the crowbar circuit has no zener diode by design. I think its time to put in the new boards and try it out. I can use the original heat sinks with some orientation changes and new holes drilled. I'll be back
 
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