Folsom's great little 7297 Chip Amp

lacro · « **Reply #680 on:** 21 Oct 2016, 01:40 pm »

I think Jeremy wants to see the area under the input caps (the big blue ones) Also, you should clean up the residue on the bottom (and top) of the board with alcohol and Q-tips. Trim the component leads down to the top of each solder peak. Then using powerful magnification such as a jewelers eye loupe, inspect each solder joint for a possible cold solder connection.

Folsom · « **Reply #681 on:** 21 Oct 2016, 04:02 pm »

Correct.

So far it should turn right on, and does up until the chip, so we need to know why you don't have music.

Folsom · « **Reply #682 on:** 21 Oct 2016, 04:04 pm »

I assume the negative terminals for the output to speakers are indeed isolated from chassis, correct?

KR500 · « **Reply #683 on:** 21 Oct 2016, 04:32 pm »

Pomona binding posts with plastic on each side of the chassis

Yes

KR500 · « **Reply #684 on:** 21 Oct 2016, 04:44 pm »

I think Jeremy wants to see the area under the input caps (the big blue ones)
some q-tip fluff to be cleaned off and thanks for letting me know about that Larry , wasn't aware of that . I hadn't trimmed off the leads yet since there was an issue somewhere

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Folsom · « **Reply #685 on:** 22 Oct 2016, 07:13 pm »

Did the chip receive abnormal amounts of heat?

I see no reason why you shouldn't be listening to music.

You didn't drill any holes did you?

KR500 · « **Reply #686 on:** 22 Oct 2016, 07:26 pm »

No and no
The chip soldered on pretty easily and the joints on each leg look okay on both sides of the board

BRN · « **Reply #687 on:** 22 Oct 2016, 08:41 pm »

What about the potentiometer? How is that wired? If it is not wired properly it could be the problem.

KR500 · « **Reply #688 on:** 22 Oct 2016, 08:49 pm »

BRN , my suspicions today also , I may have wired it in the opposite way from the picture diagram although I have wired DACTS/pots before
I'll flip them and see

zek · « **Reply #689 on:** 22 Oct 2016, 10:05 pm »

KR500 · « **Reply #690 on:** 22 Oct 2016, 11:02 pm »

DACT wired backwards. I copied down a diagram from a web site on wiring connections .
Switched to proper terminals, and still nothing

Folsom · « **Reply #691 on:** 23 Oct 2016, 12:11 am »

Dead silence when on?

KR500 · « **Reply #692 on:** 23 Oct 2016, 01:08 am »

Yes, I gotta take a break and look at it again tomorrow
Going to take our granddaughter to the Haunted Pumpkin field Of Fear tonight and re-check .

KR500 · « **Reply #693 on:** 26 Oct 2016, 04:58 pm »

finally got a moment to re-check and
I assume the negative terminals for the output to speakers are indeed isolated from chassis, correct?
The Pomona binding posts have ridged plastic collars on each side of the chassis panel, but don't isolate the post completely from the chassis
I removed the four binding posts from the chassis and one channel works ,but not the other channel for some reason .
Back to troubleshoot that and figure how to isolate the binding posts from the chassis

Folsom · « **Reply #694 on:** 26 Oct 2016, 06:10 pm »

Ah! Sounds like problem solved, good job, just a little playing around now.

I thought the plastic had a shoulder or something to go into the hole sort of like the one at the chip?

lacro · « **Reply #695 on:** 26 Oct 2016, 08:09 pm »

Quote from: KR500 on 26 Oct 2016, 04:58 pm

finally got a moment to re-check and
I assume the negative terminals for the output to speakers are indeed isolated from chassis, correct?
The Pomona binding posts have ridged plastic collars on each side of the chassis panel, but don't isolate the post completely from the chassis
I removed the four binding posts from the chassis and one channel works ,but not the other channel for some reason .
Back to troubleshoot that and figure how to isolate the binding posts from the chassis

Only one channel working? Not sure which Pamona binding post you have, but look at the drawing at this link: http://www.mouser.com/ds/2/159/d3750_60_70_1_01-34263.pdf. The 2 plastic washers have a step in them. If you drill a 3/8" hole the step from each plastic washer will fit the opening preventing the washer from moving side to side. Did you drill a 3/8" hole or just one large enough for the threaded shaft?

KR500 · « **Reply #696 on:** 26 Oct 2016, 08:36 pm »

I thought the plastic had a shoulder or something to go into the hole sort of like the one at the chip?
Yes that's right , and I thought.... gee that's slick and drilled a small hole that the post went in, but not the shoulder .
Good thing I'm not working on the space program !
Thanks for the link Larry, I need to read the spec sheets for sure

KR500 · « **Reply #697 on:** 28 Oct 2016, 08:13 pm »

I drilled out 3/8th holes for the binding posts, mounted them and hooked everything up and am listening to the recent UK remaster Cd of the first Procol Harum CD.
Both left and right channels are working and SOUNDING GRREAT !

Thanks to Jeremy for a cool contribution to the DIY community for us all to enjoy

I just have to drill out the some C+C vent holes on the case cover ( courtesy Lacro ) over the pcb area and find a way for the binding posts to lock in place securely before closing up .
The posts have a circular plastic shoulder with a flat portion so they won't spin but I can only drill a round mounting hole.

Odal3 · « **Reply #698 on:** 28 Oct 2016, 08:50 pm »

Glad to hear you got it sorted!

BRN · « **Reply #699 on:** 28 Oct 2016, 08:53 pm »

KR500,

That is great news. I'm glade that you were able to finely work it out. I know that it can be very frustrating when you run into a problem on a build. I just built the keantoken simple error-correction superbuffer and was getting hum and picking up radio stations. I looked over everything again and again. I did additional measurements and still could not figure it out. keantoken pointed out, from the picture I posted, that I have wired the output backwards. Once I rewired the buffer it work great.

Brad