Fender Frontman 15R blown output

dowlesm · 01-08-2008, 06:02 AM

Hi, I really enjoy reading all the incredible knowledge that is freely shared on this board and have a slightly embarrasing question.

I inherited a blown Fender Frontman 15R and aside from a total waste of time it will be to fix it I still can't seem to just gut it and use the cab for a small tube amp (Yes I know that's what I should do).

The TDA 2050 Output Amp is fried. The amp just hummed when turned on and no amount of knob twiddling would affect the volume of the hum. Then the chip just sizzled and smoked so I powered it off.

Is it worth trying to fix just to get some SS repair experience? I've worked on tube amps and currently repair many forms of tube equipment but am not sure where to start on this amp. I have a schematic with test points so I guess I could just start measureing everything up to the TDA2050 (It's currently removed from the circuit board).

If you tell me to just pitch it I will.

Thanks for your help.

olddawg · 01-08-2008, 06:35 AM

First disconect the speaker. I would remove the output chip (or at least float the power rails and grounds to it) and see if everything else on the amp is fine using the pre-out or fx send. If it checks out ok, make sure the speaker isn't shorted or damaged. Then find out what a replacement IC would cost. It may be relatively cheap to replace.

dowlesm · 01-08-2008, 06:52 AM

Thanks Olddawg,

I'll check the speaker first and then see if there is an output prior to the speakers. I don't think it has an effects send due to it being a relatively cheap practice amp. It does have reverb send/return and that is probably pre-output stage.

The output chip is removed from the board right now so could I just measure the power rails into the chip connections?

I'll let you know how it goes.

Mike

Enzo · 01-08-2008, 07:16 AM

The power amp IS that chip. With it removed ther should be +/-15VDC (zener determined) for the op amp ICs, and maybe +/-25 for the TDA. Slap a new TDA2050 in there and it should work. Very rare that there is anything more wrong than simply that chip. yes, do check the speaker of course.

Twist · 01-11-2008, 12:00 AM

Mouser has the NTE version in stock.
www.mouser.com
Looks like $7.60 plus shipping. If you look around you can find the generic part cheaper.

Enzo · 01-11-2008, 01:35 AM

Digikey sells the real ones for $3.78, and have 450 of them in stock.

www.digikey.com

Stay away from the NTE stuff. it always costs more, and often is not really an exact replacement.

olddawg · 01-11-2008, 05:28 AM

Quote:

Originally Posted by Enzo

Digikey sells the real ones for $3.78, and have 450 of them in stock.

www.digikey.com

Stay away from the NTE stuff. it always costs more, and often is not really an exact replacement.

+1 Very important advice and very true.

01-08-2008, 06:02 AM	#1
dowlesm Junior Member Join Date: Dec 2006 Posts: 2	Fender Frontman 15R blown output Hi, I really enjoy reading all the incredible knowledge that is freely shared on this board and have a slightly embarrasing question. I inherited a blown Fender Frontman 15R and aside from a total waste of time it will be to fix it I still can't seem to just gut it and use the cab for a small tube amp (Yes I know that's what I should do). The TDA 2050 Output Amp is fried. The amp just hummed when turned on and no amount of knob twiddling would affect the volume of the hum. Then the chip just sizzled and smoked so I powered it off. Is it worth trying to fix just to get some SS repair experience? I've worked on tube amps and currently repair many forms of tube equipment but am not sure where to start on this amp. I have a schematic with test points so I guess I could just start measureing everything up to the TDA2050 (It's currently removed from the circuit board). If you tell me to just pitch it I will. Thanks for your help.

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01-08-2008, 06:35 AM	#2
olddawg Senior Member Join Date: Dec 2007 Posts: 498	First disconect the speaker. I would remove the output chip (or at least float the power rails and grounds to it) and see if everything else on the amp is fine using the pre-out or fx send. If it checks out ok, make sure the speaker isn't shorted or damaged. Then find out what a replacement IC would cost. It may be relatively cheap to replace.

01-08-2008, 06:52 AM	#3
dowlesm Junior Member Join Date: Dec 2006 Posts: 2	Thanks Olddawg, I'll check the speaker first and then see if there is an output prior to the speakers. I don't think it has an effects send due to it being a relatively cheap practice amp. It does have reverb send/return and that is probably pre-output stage. The output chip is removed from the board right now so could I just measure the power rails into the chip connections? I'll let you know how it goes. Mike

01-08-2008, 07:16 AM	#4
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,366	The power amp IS that chip. With it removed ther should be +/-15VDC (zener determined) for the op amp ICs, and maybe +/-25 for the TDA. Slap a new TDA2050 in there and it should work. Very rare that there is anything more wrong than simply that chip. yes, do check the speaker of course.

01-11-2008, 12:00 AM	#5
Twist Senior Member Join Date: Nov 2007 Location: Springdale, Arkansas Posts: 273	Mouser has the NTE version in stock. www.mouser.com Looks like $7.60 plus shipping. If you look around you can find the generic part cheaper.

01-11-2008, 01:35 AM	#6
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,366	Digikey sells the real ones for $3.78, and have 450 of them in stock. www.digikey.com Stay away from the NTE stuff. it always costs more, and often is not really an exact replacement.

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