2275 Amp Distortion

[Jamie Starr]

"The idle current pot at 742 will not adjust. Holds steady at .006 mv's"

Do you have the "Main" speaker button pushed in?

Yes it was. Can I assume by your question that is a problem. The right channel adjusted with it pushed in.

 

[raidermc]

Differential input pair (H701,H702) should be replaced as a precautionary repair.

 

[Jamie Starr]

Differential input pair (H701,H702) should be replaced as a precautionary repair.

I wanted to replace these, but I am not sure how to match transistors. The information I have seen online is a bit more technical then my skills. Is there a simpler way to match the transistors? Or can someone point me to a place where I can purchase them already matched online? Thank you.

 

[raidermc]

Matching is important get your self a cheap transistor checker. Real easy to use

 

[raidermc]

You will be looking at the gain on the tester and match as close as possible. Buy a dozen trans they are cheap.

 

[Steven Tate]

eBay has lots of cheap Chinese component testers with LCD screens that are accurate enough. Shouldn’t cost $20.

 

[Jamie Starr]

You will be looking at the gain on the tester and match as close as possible. Buy a dozen trans they are cheap.

My DMM has a hFE setting and a socket for the transistor legs. Is this what we are talking about? Thanks.

 

[raidermc]

Perfect that's what you need.

 

[Jamie Starr]

Perfect that's what you need.

Got it. Thanks for you help. My Mouser order arrived yesterday. I will replace the suspect parts and report back.

 

[Jamie Starr]

Hi Guys. Sorry for delay in reporting back on this repair. After receiving my Mouser order to repair the amps, my solder iron quit. Waited until Black Friday and bought another one. From my using freeze spray, the distortion disappeared when I hit H714. I ended up replacing H 701, 702, 705, 706, 707, 708, and H713 and H714. Problem solved. The distortion is gone and 2275 is running on all cylinders. Nearly finished with the restoration and I will post pics soon. Thanks TMaster for your bill of supply list.

Thanks everyone for helping me solve this issue.