Folsom's great little 7297 Chip Amp

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Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #900 on: 22 Sep 2017, 06:42 pm »
The L and R are signal, which is the center of the RCA jack. SG is signal ground, the outside of the RCA jack.

zek

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Re: Folsom's great little 7297 Chip Amp
« Reply #901 on: 22 Sep 2017, 06:46 pm »
.. SG is signal ground, the outside of the RCA jack.
Common for the L and R input signal.

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #902 on: 22 Sep 2017, 09:25 pm »
Thank you so much.

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #903 on: 22 Sep 2017, 09:26 pm »
The L and R are signal, which is the center of the RCA jack. SG is signal ground, the outside of the RCA jack.

Thank you so much. This amp is so fun to built even though I have very little knowledge about electronics  :lol:

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #904 on: 3 Oct 2017, 03:38 am »
Thank you so much. This amp is so fun to built even though I have very little knowledge about electronics  :lol:

Well, I am not surprised (see above comment by myself). I finished my amp a few nights ago, plugged it in, turned it on................and it doesn't work  :?

I took it to my father in laws place; he is an electrical engineer; and we looked it over. I am using an ANTEK Transformer  http://www.antekinc.com/as-1215/
We measured the power. I am getting 16 V AC on the Input of the PSU and 20.5 out of the PSU to the Aamp Board. Right now it seems like there is not power getting to the Amp Board but a multi meter says its there.

Everything else seems to be fine coming off the of the amp to the RCA Jacks and Binding post.. So what could be wrong, any help is appreciated. I can post more pictures later. I can always use it as a door stop I guess. I am going to go cry myself to sleep now, goodnight.




Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #905 on: 3 Oct 2017, 05:55 am »
Can I get a higher res photo of the amp board? Top and bottom.

What voltage do you get off of one of the OsCON's?

It is probably something simple. It happens.

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #906 on: 3 Oct 2017, 08:00 pm »
Can I get a higher res photo of the amp board? Top and bottom.

What voltage do you get off of one of the OsCON's?

It is probably something simple. It happens.

I will post some tonight, hope it is a small thing.

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #907 on: 4 Oct 2017, 02:17 am »
Here are some Hi Res pics hope the are useful. I am not the best solderer in the world that's for sure. I cannot measure the OsCONs right now, need batteries for my meter. I will grab some ASAP to check.

notice the part I circled. the through hole filled with solder by accident.















srb

Re: Folsom's great little 7297 Chip Amp
« Reply #908 on: 4 Oct 2017, 02:31 am »
notice the part I circled. I through hole filled with solder by accident.

It could be a problem with 4-layer boards by shorting out ground or power layers, but because I'm not seeing any circuit traces on the bottom of the board, it looks like it's probably a single layer board.

Steve

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #909 on: 4 Oct 2017, 05:39 am »
I'll keep looking but I can't tell anything obvious from these photos atm, maybe there is... Knowing the voltage of the OSCON's will tell us more.

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #910 on: 4 Oct 2017, 03:13 pm »
I'll keep looking but I can't tell anything obvious from these photos atm, maybe there is... Knowing the voltage of the OSCON's will tell us more.

Just measured the OSCON's With my meter. The voltage coming into the AMP Board is 20.5 and the OSCON's are -17.5    ------ I set the meter on 200 V range.

limits

Re: Folsom's great little 7297 Chip Amp
« Reply #911 on: 4 Oct 2017, 03:27 pm »
undertowogt1--measure from an oscon positive leg (underside of board) to negative power input to the amp board. If you have the red probe of your multimeter on the positive leg of an oscon, you should see 17.5-17.7 vdc. Also, based on your pictures, you might want to flow some more solder on the chip legs. Good luck!

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #912 on: 4 Oct 2017, 03:33 pm »
OK did it. I got 17.71

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #913 on: 4 Oct 2017, 03:56 pm »
So the problem is in the chip area, mute/stby, or inputs.

Reflowing solder and making sure none of the chip pins are connecting through solder is a good idea.

What temo do you solder at?

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #914 on: 4 Oct 2017, 04:32 pm »
Just looked at the chip with my magnify glass. looks good, no solder is touching other legs. I do see that the middle pin on the first row (closest to the chip) is

soldered on the bottom only. The top potion of the hole is not full of solder. What is that leg for? Maybe thats the isue? I will fix this tonight and see what happens. My Iron is a Weller Soldering station, its a fixed temp. not sure of the temperature.



« Last Edit: 4 Oct 2017, 07:09 pm by undertowogt1 »

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #915 on: 6 Oct 2017, 01:17 am »
Just looked at the chip with my magnify glass. looks good, no solder is touching other legs. I do see that the middle pin on the first row (closest to the chip) is

soldered on the bottom only. The top potion of the hole is not full of solder. What is that leg for? Maybe thats the isue? I will fix this tonight and see what happens. My Iron is a Weller Soldering station, its a fixed temp. not sure of the temperature.




Hi Folsom,

I was just looking at the chip soldered legs. The hole that I circled in the above image is soldered fine on the bottom of the board. What I do notice is the solder from that circled hole is just slightly touching the copper of the hole above it. It is the solder hole all by itself under the chip. Would this be an issue? Where do I look to trouble shoot the mute standby
« Last Edit: 6 Oct 2017, 02:34 am by undertowogt1 »

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #916 on: 6 Oct 2017, 04:17 am »
That little hole above it isn't a concern. The closest chip hole to it is the same thing, they're connected.

The Mute/stby is the two 47kohm resistors and 100uf cap near the chip.

Maybe make sure that there is no continuity between the chassis and the negative or positive output binding posts?

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #917 on: 6 Oct 2017, 04:40 pm »
I checked continuity of all my inputs and outputs, between the binding post and chassis. I have looked at all my solder points , nothing is touching. I am getting power to the AMP Board with the proper values. I am pretty stumped now :?. Any other recommendations. What would an experienced AMP makers next move be.
Any recommendations are appreciated.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #918 on: 6 Oct 2017, 04:57 pm »
Usually it involves looking at it forever ever and ever, thinking about it a lot... feeling insane. Doing something stupid like replacing the chip and it still not working.  :lol:

At this point you may want someone to take a look. But you already had that one engineer take a peak? Think he's up for soldering in a new chip?

Before you do that, plz double check the codes on the resistors for mute/standby. You can find resistor code things online where you can put in the colors.

undertowogt1

Re: Folsom's great little 7297 Chip Amp
« Reply #919 on: 6 Oct 2017, 05:15 pm »
Usually it involves looking at it forever ever and ever, thinking about it a lot... feeling insane. Doing something stupid like replacing the chip and it still not working.  :lol:

At this point you may want someone to take a look. But you already had that one engineer take a peak? Think he's up for soldering in a new chip?

Before you do that, plz double check the codes on the resistors for mute/standby. You can find resistor code things online where you can put in the colors.

 :o I thought they were the same resistor. Must look at this ASAP. Feeling kinda dumb, but that ok with me..........ok I looked and did the a calculator online. They are the 47k Resistors.