Laney HV 100R HEAD, 10 Way Loom Connector to Effects Board Cutting out

[Platefire]

Tore this head down today that comes on normal (sometimes) when turned on and then cuts out to a very low barly audiable volume. I hooked the exposed live chassis to a speaker cabinet and did some chop sticking after the amp cut down to it's low volume. The amp came back alive when my chop stick pushed on a 10 way connector on the effects board. I did it twice to make sure that was the shorted connection---so I think I've found the issue in this connector. As shown in the attached picture the 10 way loom/cables go from main board to reverb/effects loop board and the bad connection is where the connector connects to the effects board at rear of head.

I half way attempted to unplug the connector but the connection was tight and  didn't turn loose easily so I decided I had better ask before proceeding because I have "0" experiance with these type connectors and don't want to do any harm. So I would appreciate the voice of experiance for guideance on proceeding. My first thought was to disconnect it, look for any solder/connector problems and maybe try cleaning the contacts, re-connecting it and trying it again to see if it still cuts out. Reconmendations please! I've got the manual and schematics. In the picture the pink 10 cable(not the ribbon cable) going from board 9079_3 to board 9086_4 is the cable. Where it ties into board 9086_4 is the problem connector. Thanks, Platefire 

[sluckey]

Maybe you'll get lucky and all you have to do is reseat it.

[Platefire]

Boy, you can say a lot of stuff in one sentence sluckey    I assumed by you statement the connector should unplug like normal as I assumed it would, so I tugged, lightly jiggled it and got it to let go. Took a Q-tips and sprayed some contact cleaner on it and rubbed it on male prongs, re-attached the connector working it up and down and reseated it. Fired up the amp and played on it about fifteen minuets and it didn't cut out. That's the longest its ever gone without cutting out. So I will power it on and off several more time before I'll call it fixed but right now it's sounding and looking good! Thanks, Platefire

[Platefire]

Well it worked good for one day with mutiple tries but today it's shorting out again. I'll pull it apart again and check it a lot closer to see if I can figure whats going on. Plate

[Platefire]

Think I got it this time. I pulled the connector loose from its pins, soaked the connector and pins with contact cleaner, worked the connector up and down on the pins several times then re-seated it. That was Monday and it's Thrusday and hasn't shorted out again yet averaging 3 of 4 short fire ups test per day. Platefire

[eleventeen]

Hate to mention the possibility but it is a possibility nonetheless...If when that connector was assembled onto the mating header on the board, if too much pressure was used, the board may have flexed to the point where either a trace was cracked (on the underside of the board) Or, when the installer worked against the insertion force, if because of a slight misalignment the entire force was brought to bear against ONE PIN in the connector, then the solder connection under the board to that one pin could be cracked.

How far apart are the mounting screws/standoffs that would be the supports for the board once mechanically assembled to the chassis? If there is say a ten inch gap between those screws, if the amp was assembled by a Neanderthal in bad mood, maybe too much pressure was applied and resulting flexing of the board went beyond somebodys' limits. Of course the implication is that you'd have to remove whatever hardware is necessary to flip that board up and over and inspect its underside for a trace crack or a cracked solder connection. I realize that is a complete PITA, but there you have it.

[Platefire]

Thanks very much eleventeen

I had hoped all along someone with a little experiance with these would speak up. I've dealt with PCB boards very little and never one of these connectors. Even though it's been working for four days now my fear is I'll put it all back together and it will start shorting again but I think moving it around a bit will be the ultimate test to see if it holds. I did examine it closely last time I disconnected it and no visable sign of issues with the connector and pins. Like you say, if the connection fails again it may likely be in the a board traces or solder point.

It's hard to tell by looking at the previous posted picture but the board is the effects board and is about 2" off the main top part of chassis. No standoffs. Best I can tell the board is held in place by the effects loop jacks and effect level pot through the back vertical part of chassis. This is two effects loops, side chain with bypass switch, effecs level jack, footswich jack and preamp out/power amp in jacks. So with no standoffs and only jacks holding the board, it's possible that any excessive force could have done damage. Thanks again for the info. Platefire

[eleventeen]

I think before releasing the animal back into the wild and especially while it is still apart; with power on and some kind of signal going (because the fault you report is signal cutout and not a great big static crunch--meaning you NEED the signal to detect the fault)  I would try to flex the board downwards and upwards maybe 1/8"...right in the area of that connector. See if you can get cutout. Give it just a little more force than it should ever see but nothing violent.

PC boards can generally withstand lots more flex than you might imagine, but all it takes is one trace, maybe a little thin on the plating, that somebody accidentally scored with the blade of a screwdriver during handling.

I once worked in a plant where they made OEM CRT displays...for ATMs, and those little 5" displays you used to see on cash registers. One particular model, by far the most complicated they made, used a two-sided PC board. All the others were one sided. As it turned out, the artwork between the two sides was slightly misaligned. (supplied by an outside supplier) The unit used "stand-up" type pots for V Hold, Brightness, etc; etc; and the legs for the pots ended up creating all manner of shorts to the ground plane on the side of the board where the pot connections were NOT made. These things would fail off the assy line, go back for repair 3-5-8 times. I ultimate proved that I could fix all of them by unsoldering the pots and lifting them off the board 1/32". It took 5 months of the engineers (I was just a lowly tech) laughing at me to show them what was what. The head engineer then sat me down and offered me a 25 cent per hour raise. I replied, "OK, I am going to leave work today and every day hereafter at 2 pm until I find a real job". He practically fell over. 'Course, that was LA in the eighties, and if you could show up two days in a row someplace and not smell bad, they would hire you. Nothing like today.

[Platefire]

eleventeen

I did as you said, I flexed it about 1/8" movement three times and tried it, still good signal. Think I might try it a couple more times today and if all is well sow it up. Thanks, Plate

[Platefire]

I tested the amp serveral more times and even flexed the board next to the connector again with no more short outs. Put it all back together today and tested it several more times after that with no problem! I'm calling it done for now. Hopefully it will stay. Platefire

BTW: One thing I can say about this amp, the chassis is easy to remove and manage once you get it out. Easy to reassemble. Tube sockets are chassis mounted. I'm not familiar with the strange cake looking PT with a huge bolt through chassis-new one on me. Seems pretty good build quality for PCB/ribbon cables.  

[eleventeen]

Good on ya! Well done. I am glad you did not have to go through a big disass'y exercise to flip the board over.

Ribbon connectors are for most applications *phenomenally* reliable and before people chime in and say "sez you"...amps are subject to a lot of forces that most other electronics are not...not to mention the hundreds/thousands of heating/cooling cycles. And they stick around for 30 and 40 and 50 and 60 years in the case of old Fenders so that W & T adds up. As it turns out, the fiber parts board of a traditional Fender amp is remarkably indifferent to "road" abuse. As in the case of so many things from Fender...they built it the way Leo thought it should be built which was lots more low-cost than mil-spec and it just turned out that way.

[Platefire]

Har! Every old fender I open up the fiber board looks like waves on the sea but they keep working perfectly in most cases. I sure like the turrets and turret board like Doug sells a lot better. Pretty sturty stuff. Plate