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PostPosted: Wed Jun 08, 2022 9:15 am 

Joined: Wed Jun 08, 2022 9:00 am
Posts: 1
Hi All,
I finished the 27v Boost build today, super fun. That said, I am having an issue very similar to the posts below. In short, no issues when bypassed, but when engaged, I get extremely garbled sound when strummed very hard, and no sound at normal playing intensity. The LED works without issue when engaged.



Based on what I found there, I resoldered a few joints that looked dicey, and then measured IC voltages. Here is what I found, which leads me to believe the 7660S is bad:

1: 4.59
2: 4.59
3: 3.74
4: 4.5
5: 4.54
6: 4.59
7: 4.59
8: 8.18

1: 9.16
2: 9.16
3: 0
4: 7.10
5: 9.16
6: 8.10
7: 8.49
8: 6.94

Does my diagnosis check out? I can get some pictures if necessary.

PostPosted: Wed Jun 08, 2022 11:30 am 
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Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5639
Location: Moses Lake, WA
The 7660 definitely appears to be the most likely culprit. If you tack a jumper wire to the 3 and 5 pins of the 7660, it will provide ground to pin 4 of the TL072. It will no longer be a "27V" boost. It will be a 9V boost. So it should "work", it just won't have as much headroom. If this is the case, then I think it would be safe to assume that the 7660 is definitely the problem and you should contact for a replacement.

*patience is a virtue*

Please do not PM me. email is prefered.

PostPosted: Wed Jun 08, 2022 11:36 am 
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Joined: Tue Jan 02, 2007 1:24 pm
Posts: 15547
Location: Albany, NY
Some of those voltages should be negative and it's easy to overlook the negative sign on a multimeter display when taking DC voltage readings. Are you certain that all of those readings are correct? Also, the pin numbering is critical to interpreting the results, so please confirm that your readings correspond to the left side of the image below:


Photos are always appreciated!

“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

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