LP1502iq - bridge (?) to be replaced

I opened my Linear Power 1502iq and noticed that a bridge (on the mainbord is br1a1)) is cocked (overheated) - the component is labelled ctu-2r 29302.

I have not found any info googling around while I can find info on the other one (br1a2 on the mainboard) labelled GI FEP16ct 9010.

What can be used to replace it?

It looks like it's the only component that have to be replaced - amp is working but claerly not 100%

btw - anyone has the schema of the ampli?

Thanks
 

shagone

Member
2007-04-11 9:42 pm
those should be your positive and negative rectifiers (dual diodes) for your main positive and negative rail voltages. most 16amp rectifiers in the same TO-220AB package should work fine. remeber one is positive and one is negative. i would change both i were you and investigate why it blew. check for shorted caps and shorted stransitors in the power supply.
 
shagone said:
those should be your positive and negative rectifiers (dual diodes) for your main positive and negative rail voltages. most 16amp rectifiers in the same TO-220AB package should work fine. remeber one is positive and one is negative. i would change both i were you and investigate why it blew. check for shorted caps and shorted stransitors in the power supply.


Yes, there are two of them, one for each side - one positive and one negative.

I have inspected the amp and all looks OK - amp is working. It's just the rectifier that looks coocked but still working.

Thanks also to Perry.
 

shagone

Member
2007-04-11 9:42 pm
manina said:



Yes, there are two of them, one for each side - one positive and one negative.

I have inspected the amp and all looks OK - amp is working. It's just the rectifier that looks coocked but still working.

Thanks also to Perry.


when you say it looks "coocked" in what way? is there black soot around it? have you checked it for shorts with a multimeter? it could just be old dried up flux on the board. you could always clean it up ad remove all the old solder and add new solder.

check your positive and negative rail voltages. are they close to the same besides the + and - ? be sure to have the board mounted to the sync while testing or the amp could overheat fast, especially an older one like this.

you could also post a photo for us to see.
 
shagone said:



when you say it looks "coocked" in what way? is there black soot around it? have you checked it for shorts with a multimeter? it could just be old dried up flux on the board. you could always clean it up ad remove all the old solder and add new solder.

check your positive and negative rail voltages. are they close to the same besides the + and - ? be sure to have the board mounted to the sync while testing or the amp could overheat fast, especially an older one like this.

you could also post a photo for us to see.


With "coocked" I mean that the top metal is turned to yellow while all the other elements are still of the original "metal" colour. Tomorrow I'll take a picture
 
manina said:



With "coocked" I mean that the top metal is turned to yellow while all the other elements are still of the original "metal" colour. Tomorrow I'll take a picture


Here it is a snapshoot with the rectifier circled -
 

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If the amp works, then don't worry about the rectifiers. Rectifiers either work or don't (in this application). When they fail on these amps, they short out completely and the amp won't turn on. If the amp still has problems, look elsewhere.

These rectifiers are FEP16 (positive voltage, dual diode fast-recovery modules) or FEN16 (negative).

The coloring you see on the tab of the FEP device is red felt pen used to differentiate the positive and negative (used black felt pen) devices to simplify board assembly.

The 1502iq amp is the same as their 952 amp (with some PCB tweeks and a speaker relay installed) with the rail voltages bumped up to gain spome power and to gain some sales dollars.

I'll see if I can post the 952 schematics later. I just replied to a post on a 2002 amp in this forum a bit earlier.
 
DCPreamp said:
If the amp works, then don't worry about the rectifiers.

<cut>


I'll see if I can post the 952 schematics later. I just replied to a post on a 2002 amp in this forum a bit earlier.

Actually, the amp does not work at its best. When I turn it on, it has a metallic sound
however after 10-15 minute of work it sounds as it should be. :bawling:

I targeted the rectifier hoping it was it as it' a pretty easy job to replace this one but if you say it' either working or not, I have to come back to the first option: caps to be replaced


If you have also the 5002iq schematic will ge great;)
 
Here are the 1502 amplifier schematics. The power supply will follow.

As far as the "metal" sound, I'd need to see the waveforms to diagnose it. I still don't think it's the rectifiers, and doubt it's the caps either. It may be the bias circuit: It could be running a real harsh class 'B' until the amp warms up to A/B.
 

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DCPreamp said:
Here are the 1502 amplifier schematics. The power supply will follow.

As far as the "metal" sound, I'd need to see the waveforms to diagnose it. I still don't think it's the rectifiers, and doubt it's the caps either. It may be the bias circuit: It could be running a real harsh class 'B' until the amp warms up to A/B.


Thanks for the PDF (all you posted :D ).

I'm not able to provide the waveforms - don't have the equipment for this.

As long as it's a matter of replacing caps I can do it by myslef - I'll have to find a good technician to adjust the bias.
 
work almost done

It has been a while since the last post. I finally managed to have time to work on this amp :smash:

Changed all electrolites caps, fixed some soldering (especially at the rele side) and changed the power cables with longer/bigger ones.

I also moved the trimmer to regulate the polarization and finally the amp works great.

How can I fine tune the polarization? I did it "by ears" - slighlty turned untill it sounded better hower I understand this is not the best method; any suggestion?:confused: