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Realistic APM-200 dead

N

newclassA

Member
Hi,
I have an APM-200 which do not do anything when plugged in, looks like the power transformer is dead. The transformer has a dual phase AC output but I am not sure about the voltage. I think, I have seen the lamps are 12v, so could it be a 12v-0-12v output. Also the power and watt switches are broken, does anyone know a replacement or how to reconstruct them. Thanks in advance for your inputs.
 
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There will be likely more than one secondary. It isnt too common for a power trafo to die.

Go to hifiengine.com, register and download the service manual there if its you can find it.

Read that to get an idea of the wire colours and where to measure AC output at the secondary's with a meter.

First check the mains fuse also. If there is no output from the mains trafo then it could be a problem with either mains voltage selector (if fitted) or a thermal fuse which may be mounted inside the actual trafo windings.
 
Thanks, avionic and slimecity.
The transformer is dead in the primary. Secondary has two phase. I have checked the schematic but i don't see (or don't know how to decode) any number for voltage. The lamps are 12v (from reading other post), so one phase is ~12vac, not sure about other. However I have ordered one that has 12v-0-12v, will see what hapens when I put that in. In the mean time any ideas and suggestion are welcome.
Edit 1: trying to post a picture.
 
greetings;
Look at the unit ac wattage label rated and size of diodes in the rectifier main cap(s) rating, should give you a hint. if any v's in the schema would help ball park a replacement, too
 
Binkman said:
Look at the unit ac wattage label rated and size of diodes in the rectifier main cap(s) rating, should give you a hint. if any v's in the schema would help ball park a replacement, too
Click to expand...
Thanks.
It's rated as 7W. I have attached some picture of the circuit board.
 
newclassA said:
The transformer is dead in the primary. Secondary has two phase. I have checked the schematic but i don't see (or don't know how to decode) any number for voltage. The lamps are 12v (from reading other post), so one phase is ~12vac, not sure about other. However I have ordered one that has 12v-0-12v, will see what hapens when I put that in. In the mean time any ideas and suggestion are welcome.
Click to expand...
Transformer secondary is center-tapped. Each side AC powers one lamp. Looks like a reasonable case for 12V-0-12V.

D21 in the voltage regulator circuit is a 12V zener. Should provide about 11.4VDC to load after drop across Q7.

apm200-ps-c.jpg

[edit] Added a little colour for drama. Couldn't resist ... :)
 
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newclassA said:
Also the power and watt switches are broken, does anyone know a replacement or how to reconstruct them.
Click to expand...
Online this morning ordering parts and the mind wandered to this thread. APM-200 switches look similar to those in a Realistic SA-10 amplifier:

Switches_APM200.jpg
Switches_SA-10.jpg

SA-10 has DPDT slide switches. If APM-200's are also slide, rather than toggle switches with levers that pivot, they might be interchangeable with those from an SA-10.

Against the odds of finding an APM-200 or SA-10 parts donor, there are few sources for switches with round levers. UK's RS carries something similar, but without a black styling effect at the tip. Australia's Jaycar Electronics and South Africa's Communica each stock a product with a styling effect of sorts. Actuator shafts of all examples above seem a bit short.

Closest prospect might be from US based Electronic Surplus. Matching any candidate will be a matter of taking careful measurements of the stock part: mounting hole spacing, connection terminal configuration, shaft diameter and length, etc.

So how broken are the stock switches?
 
Stuart Pedaso said:
So how broken are the stock switches?
Click to expand...

Thanks.
Well, the back PCB came out from claw but the main problem is the metal contact that closes the circuits are missing on both. I have seen on bay the 2P2T is are available in generic form and few other vendor has with similar looking knob, I did not compare the size yet.
 
eizner23 said:
I am servicing an APM-200.

@Stuart Pedaso can you share the APM-200 schematic with us? Thanks.
Click to expand...

I pinched the schematic from a copy of the Instruction Manual posted at hifiengine.com.

It might not be proper to repost in its entirety here, and I should have referenced the source in post #8 above.

The manual can however be downloaded for free after registering an account at hifiengine -- also free.
 
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