Ensoniq SQ-80 Front Panel Button Problems - Please Help

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flpfire109
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Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Wed May 06, 2020 5:25 pm

Hi All,

This is my first post here so please forgive me if I have posted this in the wrong place or not followed the posting procedure correctly. I tried searching for other similar posts on this issue, but could not find anything.

Anyway, I am helping a friend to fix his Ensoniq SQ-80. It's in beautiful cosmetic shape, but had a couple minor issues (so I thought). The battery was nearly dead and 5 of the tact switch buttons on the face of the unit do not work. So, I replaced the battery hoping that may be causing the button issues... it wasn't.

So then I figured that the tact switches for those buttons must have gone bad. I ordered replacements from Syntaur that came in yesterday. However, last night I replaced all 5 of what I thought were faulty tact switches, but the problem still persists. The buttons for Bank number 4, soft button number 4 above the screen, along with envelope buttons 1,2, and 3 still do not work. The sequencer stop button may also not be working. Does anyone have any ideas? The synth does work and sounds great now otherwise.

Also, I briefly checked the traces, they looked good. I did notice this thing (resistor?) soldered to the bottom of the display board. It seems like an afterthought. Is this factory installed?



Please feel free to ask any questions for clarification. I have the synth open and can take more pictures too, if that would be helpful for diagnosis. Thanks to this community in advance!!!

Jack
Last edited by flpfire109 on Wed May 06, 2020 9:42 pm, edited 2 times in total.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Wed May 06, 2020 7:55 pm

So, I have done more research and there is a very similar post on here from 2017 titled "Ensoniq ESQ-1 local keyboard" with almost the exact same issue. However, obvious the model in question in that case is an Ensoniq ESQ-1 not an SQ-80. I have one of those to reference, but it has different connections from the main board to the display board.

The SQ-80 does not have the Ribbon cable connecting the main and display boards, just 2 molex style connectors. However, I imagine that the problems are still very closely related. If anyone can point me in the right direction on where and what to look for, it would be greatly appreciated. I am a hobbyist who knows just enough to be dangerous, but I do not consider myself an expert by any means.

Thank you all in advance for your participation on these forums. Your knowledge and willingness to share it is an extremely valuable and much appreciated resource!

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Wed May 06, 2020 9:37 pm

Also, I can now confirm that the buttons in question do not work while in test mode. I believe this eliminates a software issue as the potential cause.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Thu May 07, 2020 5:19 pm

Any help here would really be appreciated!

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by Rasputin » Mon May 11, 2020 4:06 pm

flpfire109 wrote:
Wed May 06, 2020 9:37 pm
Also, I can now confirm that the buttons in question do not work while in test mode. I believe this eliminates a software issue as the potential cause.
You have a problem with ROW 7 = 4, S4, ENV2, STOP, ENV1, ENV3

Get the SQ80 keypad schematics from here:
http://zine.r-massive.com/ensoniq-techn ... chematics/

Other than the trace, points of interest are C23 and pin 11 of the 6500/11. Worst case scenario is a dead 6500 because they are not a generic part and no longer manufactured.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Tue May 12, 2020 12:04 am

Thank you Rasputin. I really appreciate your help. I will check out row 7 this evening. Hopefully as you said, it's not a dead 6500.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Tue May 12, 2020 6:30 pm

This may be a dumb question, but I am just a hobbyist, not a skilled technician. I cannot find C23 anywhere on the display board. The caps on the display board stop at 22. Also, my board is a revision A board, while these schematics are for revision C.

Is C23 located underneath the display itself or on another board within the unit?

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by Rasputin » Tue May 12, 2020 10:30 pm

flpfire109 wrote:
Tue May 12, 2020 6:30 pm
Also, my board is a revision A board, while these schematics are for revision C.
The schematics are good for the purposes of illustration, but you don't even need them to test this issue. All you need is the general concept of how the problematic buttons are tied together. Since we know all the non-working buttons are tied together to the same row, just look at the board itself to find the trace that connects those specific switches to the same point.

Use a multimeter to check for continuity. Assuming the keyscan chip is not dead on that one pin, there will have to be a break in the trace (or bad solder job, etc.) between the pin that connects to all of those switches.

You can even use visual inspection to follow the trace around the board. Once you see how there is one trace which connects all the bad buttons and that it leads back to one point on the keyscan chip then it should be clear what to do.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Wed May 13, 2020 7:30 pm

Well unfortunately, it does look like the Rockwell 6500 is at fault. The whole length of trace and all of the switches pass the continuity test.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by Rasputin » Thu May 14, 2020 2:36 pm

flpfire109 wrote:
Wed May 13, 2020 7:30 pm
Well unfortunately, it does look like the Rockwell 6500 is at fault. The whole length of trace and all of the switches pass the continuity test.
It wouldn't be the first time, but double-check that there isn't a bad solder joint on the 6500 or something shorting that pin, etc.

I would check that the capacitor which serves that row is functioning properly (in the same way that the other rows work).

If it seems like the 6500 does truly need a replacement, try contacting Rainer at http://www.buchty.net/

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Thu May 14, 2020 8:52 pm

Rasputin I seriously appreciate all of your guidance on this. I cannot thank you enough. Regarding the cap, do you have any idea where it is located? The caps on the display board are numbered through C1 - C22, but nothing further. I cannot find C23. Could it be mounted underneath the display? There looks to be what looks to me like several test points on the underside of the board.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by Rasputin » Fri May 15, 2020 12:56 am

flpfire109 wrote:
Thu May 14, 2020 8:52 pm
I cannot find C23.
The schematics are a red-herring of sorts because your revision of the display board doesn't match. The components will be numbered differently, although the concept is still the same.

GENERAL TROUBLESHOOTING CONCEPTS FOR ENSONIQ SQ80 KEYPAD FAULTS

Ensoniq SQ80 Key Matrix (7x8 allowed, 51 used)

COLUMN 6 = x, x, x, x, x, SPLIT, MODES, DCA4
COLUMN 5 = ENV3, ENV4, FILTER, LFO3, LFO2, DCA3, DCA2, DCA1
COLUMN 4 = ENV1, OSC3, OSC2, OSC1, PLAY, LOCATE, CONTROL, MIDI
COLUMN 3 = STOP, MIX, EDIT, STORAGE, REC, SELECT, CREATE, MASTER
COLUMN 2 = ENV2, LFO1, S5, S10, S9, S8, S7, S6
COLUMN 1 = S4, S3, S2, S1, WRT, DOWN, UP, CMP
COLUMN 0 = 4, 3, 2, 1, INT, CARTB, CARTA, SEQ

ROW 7 = 4, S4, ENV2, STOP, ENV1, ENV3, x
ROW 6 = 3, S3, LFO1, MIX, OSC3, ENV4, x
ROW 5 = 2, S2, S5, EDIT, OSC2, FILTER, x
ROW 4 = 1, S1, S10, STORAGE OSC1, LFO3, x
ROW 3 = INT, WRT, S9, REC, PLAY, LFO2, x
ROW 2 = CARTB, DOWN, S8, SELECT, LOCATE, DCA3, SPLIT
ROW 1 = CARTA, UP, S7, CREATE, CONTROL, DCA2, MODES
ROW 0 = SEQ, CMP, S6, MASTER, MIDI, DCA1, DCA4

- Each switch is at the intersection of one column and one row.
- If one row fails then it will take out every switch connected to that row.
- If one column fails then it will take out every switch connected to that column.
- If only one or two switches have failed then it must be the tact switch, or a small section of bad trace.
- If three switches fail then it's probably still the tact switches unless it's the SPLIT, MODES, and DCA4 switches (in which case it's most likely electrical).
- If 4 or 5 switches fail then at least one tact switch must be bad, or a small section of bad trace.
- If 6, 7, or 8 switches fail then it's very, very likely electrical.
- If any of the column pins (13~19) on the 6500/11 fail then an entire column will go out.
- If any of the row pins (4~11) on the 6500/11 fail then an entire row will go out.
- Likewise, if there is a bad trace between a column or row pin on the 6500/11 and any switches than an entire column or row will go out.
- If any of the column or row pins on the 6500/11 have a cold solder joint then that entire column or row will go out.

- There is one diode and one capacitor for each COLUMN line.
- There is one capacitor for each ROW line.

The capacitors all have one leg connected to ground. If a capacitor fails short then that entire column or row will be pulled to ground and will never be able to go high. This will cause the entire column or row to go out.

In your case, the dead buttons all correspond to one specific row, so we know that either the peripheral circuit for that specific row is bad somewhere, or the 6500/11 pin related to that specific row is bad.

If there is continuity from the row 7 pin to all the switches on that row then it's not an interrupted trace. The diodes are only on the columns, so it cannot be those. That suggests either that pin on the 6500/11 is internally faulty, or something externally is pulling it permanently high or low so that it cannot change states.

In short: Follow the row 7 line from the 6500/11 and it will lead you directly to the capacitor in question. See if that capacitor is shorted to ground. Do the same with some of the other rows. If the capacitor for row 7 behaves differently than the capacitor for the other rows then that would be a big red flag.

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Fri May 15, 2020 6:12 pm

Thank you Thank you Thank you for your detailed instructions! I am soo eager to learn and build my skillset, but I don't have a ton of confidence yet working through troubleshooting on this level. I will go through this in detail tonight when I get off of work. I know I have said this already, but you are MUCH APPRECIATED!

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by flpfire109 » Sun May 17, 2020 7:38 am

None of the caps on the board are shorted to ground. The only possibly odd thing I noticed is that one of the 3 large caps on the board does not seem to be connected to ground on either side. I've attached a photo with the cap in question circled in red on my photo of the top side of the board.

However, I still can't locate which specific cap ties in with row 7. Row 7 is connected to pin 11. The trace leaving pin 11 immediately brakes off in two separate directions. However, there is not a cap in line on that trace going either way. The caps all seem to be connected together via a large "bus" (my description, likely not the correct term) trace that runs underneath all of the chips. I have circled this area in blue on my solder side photo. There is an area on the board where it looks like it was designed for caps to have been soldered in line, but there are no caps mounted on either side of the board there. I have circled this area in red on my solder side photo.

Maybe I am totally misunderstanding something?
Attachments
IMG_20200516_230203.jpg
IMG_20200516_214933.jpg

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Re: Ensoniq SQ-80 Front Panel Button Problems - Please Help

Post by Rasputin » Sun May 17, 2020 9:12 pm

flpfire109 wrote:
Sun May 17, 2020 7:38 am
Maybe I am totally misunderstanding something?
Probably not. All I've had to go by is schematics, and those schematics aren't even 100% for your board revision :D

It's entirely possible that almost all of the little caps are decoupling caps for the ICs. And the cap which has one leg not connected to ground is not likely a problem either. The capacitors I was expecting to see could have just been added to mitigate switch "bounce" to prevent false triggering, so not surprising that they might just not be there on earlier boards.

Unfortunately, it's fairly likely that the 6500/11 is simply faulty. I was hoping to rule that out with a "hail mary" but those chips have a bad reputation for going belly-up. Truly annoying to have a 99.9% functional machine without an easy way to repair it.

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