Folsom's great little 7297 Chip Amp

KR500 · « **Reply #620 on:** 27 Sep 2016, 09:07 pm »

I put the jumper on between tabs for #8 and #11 on the Hammond Transformer and wondered how folks are wiring the N leg of the AC connector to 2 separate tabs ( #1 and #5 ) on the transformer ?
I looked at Jeremys photograph but couldn't really see how both connections were made with one wire .
thanks

BRN · « **Reply #621 on:** 27 Sep 2016, 11:14 pm »

KR500,

I wired it with 2 wires connected to a quick connect going to tab 1. One wire went to the N leg and the other went to tab 5 with a quick connect. I did the same thing for tabs 2 and 6.

The power switch I used for my build was a DPST, so both wires from the IEC went to the power switch.

I hope that helps.

KR500 · « **Reply #622 on:** 28 Sep 2016, 12:45 pm »

Thanks BRN ;
Today I'll head over to Home Depot to see if they have disconnects for 10-12 size, the 14-16 disconnects I currently have on hand accept the 14 gauge solid I'm using for AC but not 2 .
I've used two wires in one disconnect before but only in speaker crossovers with 18 or 20 gauge wire

lacro · « **Reply #623 on:** 28 Sep 2016, 02:05 pm »

Quote from: KR500 on 28 Sep 2016, 12:45 pm

Thanks BRN ;
Today I'll head over to Home Depot to see if they have disconnects for 10-12 size, the 14-16 disconnects I currently have on hand accept the 14 gauge solid I'm using for AC but not 2 .
I've used two wires in one disconnect before but only in speaker crossovers with 18 or 20 gauge wire

These work good for what I think your trying to do.

pocomo · « **Reply #624 on:** 29 Sep 2016, 01:23 pm »

Hi Guys -

With my solder slinging skills being slim-to-none my chances of completing this project successfully were essentially zero. However, with all the rave reviews I am very interested in trying out one of these amps. Does anyone have a completed amp that they would consider selling?

Thanks.

KR500 · « **Reply #625 on:** 5 Oct 2016, 12:43 pm »

On the diagram for 7297/Antipole connections the center ground post for the IEC input connector marked "E" is not connected to anything. Do you connect this to a chassis ground nut/bolt ?
correction- I printed out the connections sheet on B+W laser printer for the work bench area and it didn't reproduce the clearly marked gray E connection for ground

Also , my SPST switch has a 1 and 2 terminal that looks like the diagram picture , ......except upside down . Does the IEC connecter marked "L" get connected with the #2 terminal of the switch ?
I know these are super basic questions but I haven't wired a switch before and want to do it correctly
thanks

lacro · « **Reply #626 on:** 5 Oct 2016, 02:18 pm »

KR500 · « **Reply #627 on:** 5 Oct 2016, 04:59 pm »

Thanks Lacro for the post/pic . Earth center pin to chassis nut/bolt. Check
Looking at the earlier posted diagram for connections it looks like the SPST switch marked 2 for output is wired to the "live" right pin on the connector marked L and the transformer output from #2 and #6 connected to switch input pin 1 ? Sound correct ?
I guess my confusion surrounds the unmarked terminals of the switch in both your picture and the one Jeremy posted
thanks

BRN · « **Reply #628 on:** 5 Oct 2016, 06:34 pm »

The switch is not as critical since it is either open or closed to break or complete the connection to the power transformer.

KR500 · « **Reply #629 on:** 10 Oct 2016, 05:34 pm »

Thanks Lacro and BRN for your help
- I had printed out the connections sheet on B+W laser printer for the work bench area and it didn't reproduce the clearly marked gray color E connection for ground. Doh !
I got the LED and resistor Lacro recommended for the light switch and see he wired it to the AUX terminals on the Antipole .
Would that be the small terminal solder holes between the big caps marked 22 gauge ?
Is it an option to wire the LED and resistor positive connection to the power SPST switch instead of the Antipole ?
Does the LED negative leg then get wired to the IEC "N" terminal if you use the switch for positive ?
thanks again for your help

lacro · « **Reply #630 on:** 10 Oct 2016, 07:30 pm »

Quote from: KR500 on 10 Oct 2016, 05:34 pm

Thanks Lacro and BRN for your help
correction - I printed out the connections sheet on B+W laser printer for the work bench area and it didn't reproduce the clearly marked gray color E connection for ground. Doh !
I got the LED and resistor Lacro recommended for the light switch and see he wired it to the AUX terminals on the Antipole .
Would that be the small terminal solder holes between the big caps marked 22 gauge ?
Is it an option to wire the LED and resistor to the power SPST switch instead of the Antipole ?
Does the LED negative leg then get wired to chassis ground.... or something different ?
thanks again for your help

The LED/resistor I used was connected to a SMPS delivering 24VDC. The Antipole which I didn't use on my first build delivers around 21VDC so the LED resistor value for the Antipole will be a little different, but the one you have will probably work fine.

Powering the LED from the 22ga holes is a good idea (+-). You use both plus and minus holes to power the LED. Don't connect the negative LED lead to chassis ground. Your switch should only be turning on/off the high voltage AC (120V) input.

KR500 · « **Reply #631 on:** 10 Oct 2016, 10:40 pm »

Thanks for your help Lacro , Antipole power for LED it is .
posting your info on mounting the LED was helpful . I was able to drill out the OEM acrylic display on the NABU surplus case for the power switch and DACT and a small inside flared hole that allows for press fit of the LED.
coming down the home stretch
I'll post some pics next week after finishing up

KR500 · « **Reply #632 on:** 12 Oct 2016, 06:26 pm »

Just wrapping up and wondered where the DACT ground #1 terminal gets soldered to ? pcb ground ?
On the connections layout picture the RCA inputs are wired to the 7297 amp pcb input.
I'm assuming that if you are using the DACT pot you would connect the RCA positive output to DACT terminal 3 and DACT terminal 2 to amp input positive ?
thanks

Folsom · « **Reply #633 on:** 12 Oct 2016, 07:45 pm »

DACT's are numbered? I don't follow. Anyways if you're making an integrated unit:

Center is output on a DACT. One center pin is right, the other left (your choice, based which you chose on the input for R/L). That goes to the amplifier input. (R and L on each side of SG on the PCB board)

The input to the DACT is either on the right or left of center, depending on which direction you want it to turn for volume. Generally if you're looking at it from the back you'd place it on the left.

Then all the grounds from the input and output would go on the right two pins (for R and L). (SG on the board, and the ground tabs of your RCA jacks)

KR500 · « **Reply #634 on:** 12 Oct 2016, 08:46 pm »

Thanks Jeremy for the clarification . Just wanted to make sure I had it right before putting it all together and closing up.
I searched around online to see if I could find out the answer but only posts on the input//output wiring showed up , not the ground connection
Most posts referred to the DACT potentiometer terminals as right to left from back . I think the ebay page for the DACT I got shows that too.
3 = IN
2=OUT
1 = ground

Folsom · « **Reply #635 on:** 12 Oct 2016, 09:56 pm »

I believe what you're saying is correct.

The ground should be on the side that you want to be turned to in order to have volume all the way down.

walkern · « **Reply #636 on:** 13 Oct 2016, 02:51 pm »

If this is the version you have, here are the connections for hooking it up. The #1 position from both channels is the ground.

KR500 · « **Reply #637 on:** 16 Oct 2016, 02:00 pm »

Thanks for clarifying the ground connections Jeremy and Walker.
The IEC is grounded to the chassis
Since I attached wires on the bottom of the PCB and Antipole I went with a taller standoff . A new hole was drilled in the heat sink for the chip mount using Lacro's suggested method of turning the tap bit by hand in my drill press, then chasing the last few threads by hand . It worked out great and I slightly bent the chip legs to get it's orientation straight up.Just have to check the chip bolt with my DMM.
I installed the last part and smaller heat sink after wiring up the PCB ( 'nother suggestion from lacro ) and kept it off the board, but it still was fussy to get the heat sink to clear the resistors . I wound up bending the smaller V tab of the heat sink up to clear the 431 and sliding the sink over and crimping the clasp tight so the sink wouldn't touch the resistor . It's tight and I should have soldered the transistor even higher in retrospect.
I had left over 14 gauge solid copper wire from my garage wiring project that I used on the IEC/transformer/switch wiring . Really stiff stuff ( water and greaseproof ) and I probably just should have bought something easier to work with. HD and Lowe's don't sell it by the foot here anymore though.
No interconnects locally for 12-14 size where I had to double up AC wires on the transformer , just 10-12 and 14-16 size interconnects , crimped and then soldered the 10-12 size as they were still a tad loose.
Just have to get a knob to fit in the NABU front panel for the DACT pot.
Doh ! going over the build and realized I forgot to put an insulating washer on both sides of the chip, just have the one side of the chip . Off she comes again

Folsom · « **Reply #638 on:** 16 Oct 2016, 04:06 pm »

Why would you want one on both ides of the chip? The 7297 chip? How would you put one on the other side?

Do you mean the mica? I can see it in there, so?

KR500 · « **Reply #639 on:** 16 Oct 2016, 04:37 pm »

Folsom , I have an insulating washer on the bolt going through the chip, but thought I had to have another insulating washer on the backside of the chip ? . i.e. one on each side of the chip .
Is there just the one washer ? Just want to make sure before plugging in the unit.I made sure not to over tighten the bolt into the heat sink.
I put the DMM probe on the chip and one on the heat sink and get all zeroes at the resistance settings until I set the resistance dial down to the lowest 200 ohm setting, then I get 00.2 on the readout , same 00.2 with probes on the bolt head and heat sink
Continuity check with the probes on chip and heat sink gets a zero readout
thanks