Assembly/mechanical question RF Punch 45HD

gisewhcs · 11th February 2010, 04:31 PM

I just got a 45HD and disassembled it because I had to clean the sink and still have to drill out two of the torn off case screws (not my fault!).

When I had the PCB on my bench, I noticed a piece of foam between the PCB and the sink.
It was right under the transformer.
As somebody else obviously resoldered the rectifiers and the power connectors I'm not sure if the foam is correct there.
Wouldn't it make more sense between the transformer and the case/bottomplate to prevent the PCB from bending/hanging through?

Perry Babin · 11th February 2010, 05:02 PM

The HD amplifiers had a problem with the legs of the transistors breaking. This was due, in part, to the board moving up and down when the amp was subjected to vibration. The foam was likely installed under the most massive (heaviest) component to best damp out the motion and prevent the legs from breaking.

gisewhcs · 11th February 2010, 05:17 PM

So it really has to be placed between sink and PCB, not between transformer and bottomplate, right?

Perry Babin · 11th February 2010, 05:27 PM

IF (<< big if) it's there for the reason I suggested, placing it between the sink and the board is the most logical location for it. It requires less critical placement and it doesn't put any stress on the windings of the transformer.

I Am An Idiot · 12th February 2010, 01:05 AM

I do not remember if it were the 45 or the 75, but one of them had the pad installed directly under the BYV-XX rectifier diodes. It had to be removed to reinstall the diodes after they melted out of the board. I am thinking it was the 45. It had to be, because I do not remember the 75s melting the diodes out of the board.

gisewhcs · 19th February 2010, 08:26 AM

Perhaps my diodes weren't resoldered and they just started desoldering themselves?!

I have a bunch of BY550-50 lying around, will it be a good idea to replace the original diodes with that ones?
They can carry 5A instead of the 3,5A the BYV28-150 can carry.
Perhaps they wont get that hot to desolder themselves.

Now I've cut the foam into three pieces and put two of them next to the FETs left and right and the last piece under the transformer/rectifiers. I hope this will work!

Perry Babin · 19th February 2010, 01:08 PM

The BY550-50s aren't (from what I could find on them) high speed diodes and will run hotter and will be more likely to fail.

11th February 2010, 04:31 PM	#1
gisewhcs diyAudio Member Join Date: Sep 2007	Assembly/mechanical question RF Punch 45HD I just got a 45HD and disassembled it because I had to clean the sink and still have to drill out two of the torn off case screws (not my fault!). When I had the PCB on my bench, I noticed a piece of foam between the PCB and the sink. It was right under the transformer. As somebody else obviously resoldered the rectifiers and the power connectors I'm not sure if the foam is correct there. Wouldn't it make more sense between the transformer and the case/bottomplate to prevent the PCB from bending/hanging through?

11th February 2010, 05:02 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	The HD amplifiers had a problem with the legs of the transistors breaking. This was due, in part, to the board moving up and down when the amp was subjected to vibration. The foam was likely installed under the most massive (heaviest) component to best damp out the motion and prevent the legs from breaking. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

11th February 2010, 05:27 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	IF (<< big if) it's there for the reason I suggested, placing it between the sink and the board is the most logical location for it. It requires less critical placement and it doesn't put any stress on the windings of the transformer. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

12th February 2010, 01:05 AM	#5
I Am An Idiot diyAudio Member Join Date: Mar 2007	I do not remember if it were the 45 or the 75, but one of them had the pad installed directly under the BYV-XX rectifier diodes. It had to be removed to reinstall the diodes after they melted out of the board. I am thinking it was the 45. It had to be, because I do not remember the 75s melting the diodes out of the board. __________________ If it ain't broke Don't fix it

19th February 2010, 01:08 PM	#7
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	The BY550-50s aren't (from what I could find on them) high speed diodes and will run hotter and will be more likely to fail. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links


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11th February 2010, 05:17 PM	#3
gisewhcs diyAudio Member Join Date: Sep 2007	So it really has to be placed between sink and PCB, not between transformer and bottomplate, right?

19th February 2010, 08:26 AM	#6
gisewhcs diyAudio Member Join Date: Sep 2007	Perhaps my diodes weren't resoldered and they just started desoldering themselves?! I have a bunch of BY550-50 lying around, will it be a good idea to replace the original diodes with that ones? They can carry 5A instead of the 3,5A the BYV28-150 can carry. Perhaps they wont get that hot to desolder themselves. Now I've cut the foam into three pieces and put two of them next to the FETs left and right and the last piece under the transformer/rectifiers. I hope this will work!

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