Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => The Newcomer's Forum => Topic started by: mangokev on September 28, 2020, 12:29:14 AM

Title: Looking for help to identify and repair the circuit of my '77 5" 9v battery amp
Post by: mangokev on September 28, 2020, 12:29:14 AM
Hello,

I am new here, looking for someone that may be able to help me first identify, and then maybe figure out a way to fix the circuit board on a small portable amp I have had since I was a kid.

Attached are a couple of pictures.  It has 1/4" input on the left side, 9v mini power in on the back, and 6 C-cell battery holder inside, and a 1/4" speaker out on the back.

(http://"C:%5CUsers%5Chaklke1h%5CDownloads%5CIMG_E9409%5B1%5D.JPG")
(http://"C:%5CUsers%5Chaklke1h%5CDownloads%5CIMG_9407%5B1%5D.JPG")
(hope that's how you attach files...)

With 9V in I can measure voltage part way through the board, but the voltage get lost in the middle. 
Speaker does produce some hum/static with power on and touching the input jack.
Guitar signal in does not make it to the speaker, but pushing audio from a iphone into the in jack does make it out of the speaker but very quietly. Adjusting the amp volume in this case distorts the signal but does not increase it's volume.

Any insights appreciated.

Best regards,


Title: Re: Looking for help to identify and repair the circuit of my '77 5" 9v battery amp
Post by: flester on September 28, 2020, 05:37:29 AM
I dont see any pictures???
Title: Re: Looking for help to identify and repair the circuit of my '77 5" 9v battery amp
Post by: joecool85 on September 29, 2020, 08:24:53 PM
Quote from: mangokev on September 28, 2020, 12:29:14 AM
Hello,

I am new here, looking for someone that may be able to help me first identify, and then maybe figure out a way to fix the circuit board on a small portable amp I have had since I was a kid.

Attached are a couple of pictures.  It has 1/4" input on the left side, 9v mini power in on the back, and 6 C-cell battery holder inside, and a 1/4" speaker out on the back.

(http://"C:%5CUsers%5Chaklke1h%5CDownloads%5CIMG_E9409%5B1%5D.JPG")
(http://"C:%5CUsers%5Chaklke1h%5CDownloads%5CIMG_9407%5B1%5D.JPG")
(hope that's how you attach files...)

With 9V in I can measure voltage part way through the board, but the voltage get lost in the middle. 
Speaker does produce some hum/static with power on and touching the input jack.
Guitar signal in does not make it to the speaker, but pushing audio from a iphone into the in jack does make it out of the speaker but very quietly. Adjusting the amp volume in this case distorts the signal but does not increase it's volume.

Any insights appreciated.

Best regards,

To post an image, you need to use these "attachments and other options" link below the window where you post.  Then you can upload an image.