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VFE DragonHound and VFE SB V3 - Always In Bypass [SOLVED]

Started by Cybercow, June 13, 2022, 10:00:25 PM

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Cybercow

Did up my first VFE DragonHound with a VFE SB V3 switching board and find that it's ALWAYS in bypass. I pre-measured EVERY component before soldering it into place, so I know the values are all correct.

I know the switching board is working (except I've yet to verify the TQ2-L-5V relay) because the LED indicates whether or not it is bypass or engaged - AND - the dual-mode momentary-on option (tap-tap-hold) works inactivating or deactivating the dual-mode option.

With the unit powered up and engaged or in bypass, the input and output jacks are always shorted together.

I suspect the TQ2-L-5V. But I got them from Mouser. So the reliability of a known good relay is high. I have 9.2v at the SB V3 supply input with ~-4.5v and ~+5v at the - and + points between the two boards.

Any leads, options or something I may have missed?
Cybercow - aka: Mark Davis

"Don't let your talent take you where your character can't keep you."

Cybercow

I think I just solved it. In the SB V3 build doc, I completely overlooked the section regarding the "In the Choral Reef the following exceptions are applied" - where it says R5 & R6 are ONLY used in the "Choral Reef". As I wasn't building a Choral Reef" I ignore that bit.

Goona clip 'em out and see how it behaves. Results to follow . . . .
Cybercow - aka: Mark Davis

"Don't let your talent take you where your character can't keep you."

Bio77

It might be Q2.  That one cuts the output of the effect during switching, if it isn't working, maybe it is cutting always??

Cybercow

Bio77 - that shouldn't affect the state of the relay tho. The input and output jacks are ALWAYS shorted together, regardless of the state of Q2. I suspect the relay is misbehaving for one reason or another.

Q2 should be working. At least it tested good in my Peak Atlas DCA75.

The voltages are definitely off. I should (according to the DragonHound and SB 3V build docs) have -4.5v on the negative point and +9v on the positive points between the two PCBs. I only have ~+5.2 volts on the positive rail between PCBs. And the DragonHound board does not have +9v anywhere.

Still poking around.
Cybercow - aka: Mark Davis

"Don't let your talent take you where your character can't keep you."

Aentons

#4
V+ should be +9V
GND should be 0V
V- should be -9V

The LP2950 puts out +5V

Aentons

Here is another measurement you could take to help track it down.

From the SB build doc:
(Pin7 of the PIC is 0v in effect mode, 5v in bypass mode)

However, It sounds to me like you may have a stuck relay

gordo

I've had issues with the 2950 that sound like your symptoms.
Gordy Power
How loud is too loud?  What?

Cybercow

Quote from: Aentons on June 14, 2022, 12:34:31 AM
Here is another measurement you could take to help track it down.

From the SB build doc:
(Pin7 of the PIC is 0v in effect mode, 5v in bypass mode)

However, It sounds to me like you may have a stuck relay

Thanks. I'll check that out.
Cybercow - aka: Mark Davis

"Don't let your talent take you where your character can't keep you."

Cybercow

Quote from: gordo on June 14, 2022, 12:51:22 AM
I've had issues with the 2950 that sound like your symptoms.

I'm using the BOM alternate: LM78L05 in place of the 2950.

Still poking' around . . . .
Cybercow - aka: Mark Davis

"Don't let your talent take you where your character can't keep you."

Cybercow

Ha! A bad Zener at D2 on SB V3 switching board. I noticed how the chargepump wasn't getting +9v at all - only +5.1v

I pulled the zener and checked the number - 1N4743 - meaning it should have been a 13v Zener. When I checked my stock, I noticed how I had some from Tayda and some from Mouser. So I took one from the Mouser tape and plopped it into D2 and voila! Instant fix. I threw out the 1N4743 diodes from Tayda.

Problem now solved. Thanks and hats off to those who tossed in their 2ยข
Cybercow - aka: Mark Davis

"Don't let your talent take you where your character can't keep you."

gordo

Excellent.  Especially considering what a pig those relays are to unsolder...
Gordy Power
How loud is too loud?  What?