Tacx T2240 turbo trainer - blown resistor

Sir DaveNicko . . . . .

Am I correct in my consumption that I have found the correct portion of the affected unit, in the respect of it being the braking unit with its related
solenoids working against the steel geared wheel for creating system braking action ?.
With the associated electronics aspect, being its variable adjustable power supply, feeding to those solenoids for mag braking.

The equiipments other portion that I saw and surmised an evaluation . . . . . seems to have been a generator type of electromechanical contriviance
that used adjustable loading to it, to maintain a variable / adjustable degree of restraint, for creating a physical workout to the biker.

RELEVANT R64 RESISTOR . . . . .



By my blow up, above.
That resistor looks like its having 2 copper caps with silver overplating, as you can see by the timely blackened AgO² onset. The resistor body core is being a ceramic bisque, blank rod.
Then it is having the connection to each cap of a nichrome resistance wire . . . . being RED marked just beside them . . . . that has the bulk of the wire left intact on its "64" side. Considering that nichrome is being a quite tough and springy wire, it just might have compressed back towards that half, after burning open at its weakest point, from current overloading.

If you examine nearby, there is a white rectangular 1 amp time delay fuse marked as T1, it should be positioned / wired into the AC line input power on the "hot" side. Ohm it out as being a shorted circuit, if its being good and not blown.

I must waiver . . . without any further info or closer examination . . . . . as if your opened resistor might not have been inserted in circuit on the complete opposite side of the AC power cicuitry loop , being in line at the neutral side return of the power line.
There, the voltage developed across it is being relevant to the power consumption thru it, and that voltage level would be used as a control input for monitoring and for corrective power parameter shifting.

If that was my NUT to crack, I would see if I could get two test wire leads with their clips on each end, connected to the two end caps of the resistor. The leads other clip ends get connected to a DVM or even analog ohmmeter.
Then I use a set of small tweezers to see if I can manipulate the two burnt apart inner ends to touch just long enough to get an intact resistance reading, some scraping away of oxide may be needed at the nichrome inner wire tips.

One aspect of analysis, that you will presently be able to do, is to plug in your AC power cord in to the unit but NOT into the AC power line and then make one ohmmeter lead contact to one of the blades / pins of the male power plug and the other
ohmmeter lead is connected to one corner connection of the white F1 fuse. Is the ohmetter then confirming that there is a direct connection being made ?
If not , then try the other possibility of moving the ohmmeter lead to the OTHER pin of the male plug and do the same test to the fuse, with the other lead.
One of those connections should be directly connected to the fuse. THEN you will be able to use the OTHER unconnected male connection to receive the ohmmeter lead and then use the other ohmmeter lead to see if that connection is being made to either of the leads of the R64 problem resistor.
That test should reveal if the resisror is being conected to the "cold" side of the AC line as was earlier surmised..

If there is being no connection, then we just might expect that the R64 resistor is possibly being used at one end of another supply that is being an adjustable DC supply, being in the order of 24VDC that, is feeding those solenoid braking coils.
From an UL Underwriteres safety aspect, I can see that DC supply needing to be derived from a "cold " . . . . AC line isolated source . . . . . such as using a switch mode power supply with an ISOLATED secondary winding for producing that variable DC.
Can you give closeup pictures of that boards topside components, so that we can figure out what is REALLY being done, design wise ? Later on, the foil side, to see the wiring interconnects. The present pic only shows a portion of the top side.






73's de Edd . . . . .

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Evening, I have exactly the same problem with my turbo trainer (a TACX Smart Flow T2240). Two weeks ago its was working fine. It then sat in the spare room for 2 weeks doing nothing. When I went to use it there was no response to switching on power supply, no light at all. I took it apart this evening and noticed a small piece of material dropped out. It appears to be half of the now broken insulating material around a resistor (??). Its the same component that you have identified as a likely issue.

Did you ever get a resolution to this problem ?

 

Sir Peathaugh . . . . .


Doesn't look like the party of the first party . . . thrice removed . . . has ever come back to the situation.
In a further and deeper examining of the photo that he submitted . . . . . .
Looks like you found one of the small ringlets that had opened up in the winding of that R64 wirewound resistor . . .a fusible resistor, that is. . . . . and it definitely HAS fused out.

With it initially starting out with maybe 15 turns around its ceramic core, then blasted by overload to now having a mere half or so of its turns missing and a resultant open circuit.
So I would consider it as being in series with the hot line of the AC power coming in, that looms so ominously as that black connector at the top right front of the photo . . . . . there must be a dead shorted component in that systems supply area.



OBSERVATIONS . . . . .

Close side of the BLACK AC connector is a Matsushita surge varistor and 1 A ceramic block fuse.
Foreground has a D5 MELF type of diode and another at on the far right side rear of the BLACK AC connector and yet another at the large hole in the PCB..
And MOST importantly, is the DF10 4 pin FWB rectifier off the top of the connector. So power comes in and gets rectified by that DF10 bridge to supply the two Black electrolytics at the bottom of the board, for the basic raw DC for the supply.
With no blown T1A fuse all might be well with the DC power supply

Rest of the board . . . .
Top left corner is a 4 pin optical isolator, verifying this frontal area as being an AC "HOT" area, while thedeep, far side of the O.I. is a cold supply connected area.
Now where I think that your problem area . . .really . . . REALLY . . . .REALLY is being is the ST branded triac , between the two close in silver Torx screws.
There is also a series SM sampling resistor of 3.3 ohms connected off its MT1 or MT2 connection.
Which ties into a like other parts situation . . . . look to the top of the photo . . . . where another SM 3.3 resides, with probably yet another (grossly out of focus) power semiconductor up there . ( Is it same-same Triac? )

Read the ST's top line and confirm if that unit(s) is being a BT 200 series of triac . . . .feedback to us, all of its marking.

PROCEDURE . . . . .

Take DVM in hand and place in OHMS mode and lowest OHMS range ( unless autoranging) and ohm out between all of the 3 pin combinations of the assigned T1 triac.
Your AC power coming into this . . . . probably shorted . . .Triac apparently passes thru the already blown open R64 fuse resistor.

Now . . . . . GODOITTOIT . . . .




73's de Edd . . . . .


True Diplomacy is the ability to tell someone to "get lost" in such a way that they look forward to the trip.



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