computrainer repairs after overheating

Jan 14, 19 14:12

Post #1 of 18 (3575 views)

Longtime lurker, first-time subscriber/poster...

I have a computrainer that literally stopped working one day with symptoms where everything at the head unit appears to be correct, but when I start a warmup period (usually 6-10 minutes to facilitate roll-down calibration), as soon as I get to about 60W (measured via my quarq) the load generator clamps down HARD and I can barely turn the pedals even by standing.

The ride the evening before this failure was on zwift and was l'alpe d'huez: lots of low-cadence/high-load. I've never used a fan to cool the load generator due to ambient temps in my basement in the winter and this time was no different. Had no problems whatsoever during the session. Accidentally left it turned on overnight but with no load and not pressed against the tire.

After reading up on here, I'm wondering if it may have been a victim of overheating. And I'm wondering if anybody know what components tended to fail when a load generator overheated. Obviously racermate is no longer around to answer these questions.

I've been inside the load generator twice at this point, but only as far as removing the eddy disc. I have NOT pulled out the second board. No components show obvious signs of stress, but that doesn't mean they weren't stressed.

Hoping somebody can help me keep my LG going...

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 14, 19 14:39

Post #2 of 18 (3559 views)

Is the disc warped? Are there signs of it rubbing against anything inside?

My Blog - http://leegoocrap.blogspot.com

Re: computrainer repairs after overheating [Morelock] [ In reply to ]

Jan 14, 19 14:42

Post #3 of 18 (3549 views)

It does not rub. It is not perfectly flat, but there was no scraping prior to disassembly, nor was it difficult to reassemble with not scraping. Using my eyes, I'd guesstimate around 1-2mm air space on either side of the disc btw. the disc and the magnets.

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 14, 19 14:48

Post #4 of 18 (3541 views)

:( Did the same to mine a few months ago (link) and could never get it running smooth again. Found a replacement load generator and have been using it, but kept the old one hoping I'd stumble on a real fix.

Unfortunately sounds like you're in the same boat

My Blog - http://leegoocrap.blogspot.com

Re: computrainer repairs after overheating [Morelock] [ In reply to ]

Jan 14, 19 14:54

Post #5 of 18 (3535 views)

That makes me sad. Curious to know what you tried. Absent any direction from folks here, my next tactic is to disassemble fully to get to the inboard board and start testing the giant capacitors. I found a post on here from Racermate Roger indicating that overheating can sometimes take out an on-board fuse, but I've not yet found a fuse on the outboard board.

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 15, 19 2:47

Post #6 of 18 (3468 views)

I'm afraid I'm not much help, once things get into the electronics side I'm pretty useless. Besides checking the moving parts/adjustments, I checked the board for any burns or noticeable breaks in the solder... but I'm not smart enough on the electronic stuff to really have more than a cursory idea of what to look for. :(
Fwiw the racermate forum is not totally dead. Might be worth checking there.

My Blog - http://leegoocrap.blogspot.com

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 15, 19 3:17

Post #7 of 18 (3462 views)

There is a fuse in the transformer unit. Mine burnt out having left it on overnight. It was an easy solder. Perhaps this could be the problem?

Re: computrainer repairs after overheating [Mark57] [ In reply to ]

Jan 15, 19 6:10

Post #8 of 18 (3428 views)

Mark57 wrote:

There is a fuse in the transformer unit. Mine burnt out having left it on overnight. It was an easy solder. Perhaps this could be the problem?

*edit* read that wrong. My bad

My Blog - http://leegoocrap.blogspot.com

Last edited by: Morelock: Jan 15, 19 6:21

Re: computrainer repairs after overheating [Mark57] [ In reply to ]

Jan 15, 19 6:17

Post #9 of 18 (3421 views)

I have steered away from the power supply because everything powers up, including the head unit, and I get proper voltages from the DIN cable leads.

What symptoms did you have when the p/s fuse blew?

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 15, 19 6:19

Post #10 of 18 (3420 views)

I run mine in the basement, daily, and keep THREE smaller fans on it at ALL times. Two 8" fans (both set to high), and a pancake fan that is actually mounted to the stand. Heat is death to electronics. I may be overdoing it a bit, but it's cheap insurance. Low cadence on a long climb and I bet it was quite hot to the touch. Imagine how warm the electronics were.

I wanna go fast!

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 15, 19 6:38

Post #11 of 18 (3406 views)

For anyone interested in photos of the internals, surf on over to https://drive.google.com/...8Pio5WAp?usp=sharing

Last night's full disassembly created a new wrinkle--two of the screws that hold the inner board/cover assembly to the "U" piece of the load generator assembly were seized and the screw shaft snapped. I'll need to drill those out in order to fully reassemble. They're supposed to have been held with with loctite 242 (blue) which is designed to lubricate threads during assembly, keep threads tight while assembled, and yield under torque so low it can be generated with a reasonable screwdriver handle--but that didn't work out.

From reading up on eddy brakes online, it appears that the biggest GENERAL concern related to heat is the disc itself (the non-ferrous conductor). The stronger the magnetic fields, the greater heat generated within that item--in this case the copper disc. Granted, that disc will be near some electronics, but nothing inside shows physical signs of heat distress. Moreover, the items I'd suspect most likely to failure due to heat would be the giant capacitors, but in-circuit measurement of capacitors with a Fluke 117 multimeter indicates correct capacitance values.

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 15, 19 10:33

Post #12 of 18 (3350 views)

One easy thing to try first is a new din cable (bad DIN cables have been know to cause erratic behavior). Unfortunately to properly troubleshoot this you would need to substitute in known working parts to confirm each of your existing parts is working (hb controller, din cables, ps, load generator).

At this point it's probably pretty cheap to pick up a second unit on Ebay and then figure out what isn't working.

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 15, 19 10:37

Post #13 of 18 (3344 views)

cleeland wrote:

From reading up on eddy brakes online, it appears that the biggest GENERAL concern related to heat is the disc itself (the non-ferrous conductor). The stronger the magnetic fields, the greater heat generated within that item--in this case the copper disc.

I doubt it's a heat issue. The heat issue essentially caused warped eddy discs.

From what you are describing, my bet is on either the PS or DIN cable.

I once experienced something similar to what you described and after substituting out parts discovered it was the PS.

Re: computrainer repairs after overheating [mcmetal] [ In reply to ]

Jan 15, 19 10:47

Post #14 of 18 (3331 views)

mcmetal wrote:

One easy thing to try first is a new din cable (bad DIN cables have been know to cause erratic behavior). Unfortunately to properly troubleshoot this you would need to substitute in known working parts to confirm each of your existing parts is working (hb controller, din cables, ps, load generator).

I've substituted another head unit as well as a made-by-me DIN cable (purchased connectors & cable at local electronics place and soldered it up myself). Identical behavior regardless of head unit or DIN cable used. That leaves either power supply or load generator as the only common issues, and since everything powers up, I was inclined to think that the power supply wasn't the problem.

I suppose it's possible that my homemade cable is bad, but it seems unlikely that it would be identically bad.

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 16, 19 5:06

Post #15 of 18 (3264 views)

If you can't get another PS (or load generator) to test out, you could try changing the fuse in the PS. I once had some crazy load and eventually the fuse popped (not during that ride). Not sure why the load was so high when it was still working, but clearly something was wrong. After the fuse popped and I replaced it, it worked fine.

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 16, 19 5:55

Post #16 of 18 (3249 views)

Where are you located? I have a lightly used computrainer unit that works good except I lost the 8 pin Din cable. You can have it for $150 if you live nearby or pay for shipping.

"I swim because that's how I get to ride my bike."

Re: computrainer repairs after overheating [mcmetal] [ In reply to ]

Jan 16, 19 7:08

Post #17 of 18 (3233 views)

mcmetal wrote:

If you can't get another PS (or load generator) to test out, you could try changing the fuse in the PS. I once had some crazy load and eventually the fuse popped (not during that ride). Not sure why the load was so high when it was still working, but clearly something was wrong. After the fuse popped and I replaced it, it worked fine.

That would be totally weird, but I'll look. Right now I'm at a loss. Any chance you still know what I would have to buy to replace it?

Re: computrainer repairs after overheating [cleeland] [ In reply to ]

Jan 16, 19 9:46

Post #18 of 18 (3213 views)

It's a 1A 250V 3SB fuse. You will have to solder it in.

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