Output FETs for a Punch 150hd

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Hello all,

New to post on this forum... I didn't know there was a car audio section. I am stoked! I've got some RF Punch 150hd's that I am resurrecting from the ashes of years gone by. The output fets have long been round-filed. My question is, will some MTP33N10e fets be a good swap-in. I am checking out the on-region characteristics and they seem to be similar. I chose the 33N10e's 'cause I got 'em :). Any help would be great!

Chris

PS: Any of you guys have experience in repairing the Punch 1100a2?
 
Do you see any corrosion on the preamp board (behind the RCA jacks) components? If so, the board will need to be rebuilt (if there's not too much damage) or replaced. The ebay auction (completed auction) 170445055657 gives you the part number and the dealer. You'll have to contact him if you need one and there are none up for auction.

You'll have to try the outputs to determine if they'll work. It's generally best to use the original parts when possible because slight variations can prevent the amp from working properly. For example, the IRF540N and the IRF540 are very similar but the N version won't work in the place of the non-N version in some punch amps.
 
Thanks Ben,

I checked out the thread and it will help in the not so distant future. In the meantime, I snapped some pics of what I found just with the eyeballs...

PS: I did get one of the 150's going on the 33n10e's. Worked like a charm. As for the other one I've got, can I put 540's on the outputs? I'm all outta 33n10e's :(.

Thanks,

Chris
 

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The 540s should work in the 150.

In the 1100, it appears that the outputs failed, taking some of the source resistors which means that the protection circuit likely suffered some damage. Several of the gate resistors have likely failed also. You'll have to check virtually every SMD resistor with a value of 1000 ohms or less. Remove the output transistors from the circuit (at least cut two legs out of the circuit on each) and pull the source resistors (at least one leg on each of them) before checking the SMD resistors.
 
Hey Perry,

Question for ya'. When you referred to the "corrosion" behind the rca's on the punch150, were you referring to the leaking smt caps by chance? I started thinking, I got this 150 confused with the other. This one was a mess! It did, in fact, have "gunk" directly below the caps in the photo. I actually scrubbed this entire board with a toothbrush :eek: ! No "gunk" now...but I washed it off! On to the diagnosis:

1) Powers up great. Voltage on both rails.
2) Left channel plays phenomenal into 4 ohm load home speakers.
3) Right channel has nothing but a faint hint of audio input and static (very low volume)

Repairs so far:

1) R&R all power supply fets - Good
2) R&R all L & R 0.10 ohm source resistors - Good
3) R&R all L & R output fets w/IRF540's - Good

Any thoughts on the Left channel problems? I think I'll R&R those caps tomorrow.

Any thoughts are welcomed at this point. :confused:

Thanks,
Chris
 

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Yes, 10uF@16v sounds like the correct value.

Sometimes the corrosion eats through the vias so you have to run jumpers from the back of the board to the front.

The electrolyte also works it's way under the op-amps and the op-amps have to be removed to remove the electrolyte. This also allows you to examine the traces under the op-amp.

If the pads for the capacitors are no longer intact, it will be necessary to use leaded/through-hole capacitors. You'll have to solder the capacitor's leads to the next closest component that's connected to that trace.

If you have to use leaded capacitors, use adhesive to hold the body of the capacitor in place. Allow the adhesive to dry/cure. Then bend the leads to where they need to be soldered. There shouldn't be any tension on the leads. The pads on these boards are easily lifted.

If the trace is broken on either side of the capacitor's pads, you'll have to reconnect them. You need to confirm the connections with an ohm meter because it's often difficult to see what's open and what's intact.

It's also good to look at the traces closely with a lighted magnifying glass to confirm that the traces are full width. Sometimes they're eaten party through and will fail shortly after the amp is returned to service.
 
Hey Perry...Help...:confused::confused::confused:

I've got a couple of updates today. Turns out, the preamp audio on both channels is ok. Here's how I tested it, please correct me if I'm wrong:

***Refer to schematic enclosed***

Jumped left RCA input from true RCA input to pin 3 of HB3.
Jumped right RCA input from true RCA input to pin 3 of HB4.

Sine wave from TrueRTA plays clean on right channel.
Sine wave from TrueRTA plays "buzzy" on left channel.

:) Best description I could think of.

Where can I test now? Any thoughts...

Thanks a ton Perry,

Chris
 

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Kevlar129
Chris, where did you get the schematic, I need, would like one for Punch 300S. Right now the power and ground has a direct short, looks like from what I read in the Basic Car amp repair from Perry that I may just have a couple of bad FETs. Would love to get this fixed. Thanks for the help
Mark
 
Hey Perry,

Thanks for the reply. I guess I may have confused matters regarding the channels...
The right channel plays great from either the rca inputs or from the pin3-hb4 jump.
The left channel plays "buzzy" from either input scheme.
I do follow you in regards to possible "junk" in the upstream.
So should I isolate the left audio channel at pin3-hb3 position, to get all upstream electronics out of the mix?

Thanks for your thoughts,
Chris

Looking at the schemo again, I could isolate left channel at C9, no?
 
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Hello Perry,

Well...tried the jumper from C10 to C9 (C9 removed)...
still buzzing as if it's playing half-wave.
Upon benching it, I noticed Q1 and Q2 are heating up rapidly.
I pulled them and tested them per your website, and they seem to check out.
Drain to Source = 2.65 Mohm - is this OK?
Can't seem to figure out this da*n amp! Arg!

Thanks Perry,
Chris
 
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