Author Topic: '79 Suitcase Randomly Turns Off  (Read 426 times)

Offline Dan

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'79 Suitcase Randomly Turns Off
« on: April 12, 2019, 06:24:53 AM »
Hi, I own a 1979 Mark I Rhodes w/ the Suitcase amp, and the vibrato panel (w/ knobs, and slides for bass and treble).

Recently, I noticed that when I start playing loud, the thing will just shut off, and then occasionally come back to life. The amp makes this popping sound each time it turns back on after this. This seems to be caused by this dim 'mode' that the main red indicator led goes into. It gets dim, and in this mode, it actually blinks to the speed that the vibrato is set to, even when the vibrato is turned off. I notice that if I turn the vibrato too slow, the led will fade out entirely and the whole thing will shut off.\

Anyone know what is causing these random shut offs? I believe something inside the Rhodes is shaking and causing a short. My buddy told me it could be the original 3A fuse near the power input, he said the filament is loose. Could this be true?

Offline pianotuner steveo

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Re: '79 Suitcase Randomly Turns Off
« Reply #1 on: April 13, 2019, 04:01:33 PM »
It sounds like you have poor connnection(s) somewhere in the power section.Intermittently shutting off isn't a short, it is an open circuit. Shorts can burn out parts, blow fuses, trip breakers and in worst cases, cause fires. Open circuits are like turning off a switch. Since it seems to work when it works, this may not be that difficult to fix. What are your soldering skills? Newbie? intermediate? Expert?

It could be bad parts, but always look for the free and easy solutions first, such as bad connections in the power circuit, and bad solder connections. Unplugged, of course.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline pianotuner steveo

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Re: '79 Suitcase Randomly Turns Off
« Reply #2 on: April 14, 2019, 12:37:38 PM »
The first place I would look after unplugging from the wall is starting at the power cord socket then work your way inward. It may be a colder solder joint on a power transistor.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline pianotuner steveo

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Re: '79 Suitcase Randomly Turns Off
« Reply #3 on: April 23, 2019, 04:56:08 PM »
Any progress yet?

1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline Dan

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Re: '79 Suitcase Randomly Turns Off
« Reply #4 on: April 23, 2019, 07:32:14 PM »
Any progress yet?

I will go ahead and take off the power section on the side of the suitcase amp, and look for any cold solder joints. I have soldered many times before so it shouldn't be a problem. I'm not sure if its within the power section, due to the vibrato front panel problems, but I will go ahead and look. Hopefully I won't have to buy any new transistors or components.

Offline Dan

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Re: '79 Suitcase Randomly Turns Off
« Reply #5 on: April 23, 2019, 07:36:30 PM »
I did go ahead and purchase a new fuse from Vintage Vibe for the power section and it did seem to help for the first 30 minutes I was playing, but then it started turning off again. Usually, this only happens when I have the volume set to above 7 as well as the bass set to the max.

Offline Alan Lenhoff

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Re: '79 Suitcase Randomly Turns Off
« Reply #6 on: April 24, 2019, 09:53:14 PM »
One possibility: Suitcase pianos of this era are prone to intermittent failures caused by cold solder joints where plastic Molex connectors are soldered to the amp boards.  Read this thread and the other threads mentioned in it:  https://ep-forum.com/smf/index.php?topic=8450.msg44725#msg44725

Alan

1974 Rhodes Mark I Stage 73
1972 Rhodes Silver Sparkletop Piano Bass
1978 Hohner Clavinet D6
1968 Hohner Pianet N II
1966 Wurlitzer 140B
1967 Gibson G101 combo organ
1965 UK Vox Continental
1954 Hammond B2; Leslie 21H; Leslie 31H
1977 Fender Twin Reverb
Vox AC30CC2X amp
(SEE THE COLLECTION: https://vintagerockkeyboards.com/ )

Offline Dan

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Re: '79 Suitcase Randomly Turns Off
« Reply #7 on: April 27, 2019, 08:13:04 PM »
One possibility: Suitcase pianos of this era are prone to intermittent failures caused by cold solder joints where plastic Molex connectors are soldered to the amp boards.  Read this thread and the other threads mentioned in it:  https://ep-forum.com/smf/index.php?topic=8450.msg44725#msg44725

Alan

I think this may be exactly the problem I was having! I noticed quite a bit of distortion when hitting on the keys hard, so I think this problem could be very well linked to that molex connector. As for removing the boards, what do you recommend? It was a bit unclear in the post? Which screws do I remove for that particular board, and if I'm correct, only hot glue needs to be added to the base of the molex connector, right? Nothing needs to be re soldered?

You're a lifesaver, thank you!

Offline Alan Lenhoff

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Re: '79 Suitcase Randomly Turns Off
« Reply #8 on: April 27, 2019, 09:09:56 PM »
It's been a long time since I did this repair, and I only owned that piano for a few months. So we may need someone else to chime in on this.  But, to be clear, there are two of those Molex connectors. I believe there is one on each of two boards.  Both connectors should first be re-soldered and then given a bit of hot glue to keep the problem from repeating.

To reach the boards, I believe I removed the back speaker baffle board by removing all its screws.  Once you're in, there are plastic locking things on each corner of the boards. You use your fingertips to pinch one of them, which releases that corner of the board and lets you pull off that corner. Work your way around the board to remove it. 

Given my poor recollection of all this, I'd welcome someone who knows these pianos better to confirm -- or amend -- my instructions.

Alan
1974 Rhodes Mark I Stage 73
1972 Rhodes Silver Sparkletop Piano Bass
1978 Hohner Clavinet D6
1968 Hohner Pianet N II
1966 Wurlitzer 140B
1967 Gibson G101 combo organ
1965 UK Vox Continental
1954 Hammond B2; Leslie 21H; Leslie 31H
1977 Fender Twin Reverb
Vox AC30CC2X amp
(SEE THE COLLECTION: https://vintagerockkeyboards.com/ )