Upper body exercise bike power board bypass

OK, I've tested the diodes (removed them first) next to the blue capacitor; they're all fine. Checked the black thermistor, it's working fine.

Removed the big blue capacitor (560 uF 400v)and transistors (IRF P360 and HFA50PA60C...or is it HFA501A60C?) next to the brake power outlet connector. Not sure how to test these, any advice?

560 uF 400v . test resistance > rises exponentially not shorted

IRF360 Test resistance open D=+, S=- then with Vgs raise Gate to Source voltage 4 to 15V anywhere in this range and resistance goes down to 0.2

HFA50 use diode test or vast different resistance in both polarities

Tony Stewart said:

560 uF 400v . test resistance > rises exponentially not shorted

IRF360 Test resistance open D=+, S=- then with Vgs raise Gate to Source voltage 4 to 15V anywhere in this range and resistance goes down to 0.2

HFA50 use diode test or vast different resistance in both polarities

Click to expand...

Thanks for the answer, but can you give me step by step on that testing? I'm a complete noob. I do have a multitester with diode test function but that's about all.

Tony Stewart said:

Click to expand...

"The standard silicone diode". Really? An expert that doesn't know an elastomer from an element. (0:50, 2:05 and 3:05 marks).

Right, I did check the diodes already and they're fine. How do I check the transistors. There's a ton of youtube videos but I'm not sure what type of transistors these are MOSFET, PNP, NPN...it's all greek to me. Can anyone recommend a video that walks a noob through testing the transistor numbers I listed above?
Or...maybe someone can interpret the results for me:

Multimeter in diode test mode

IRFP360: RED lead on left terminal. No reading with Black lead on center or right terminal
Red lead on center terminal. No reading with black on left or right terminals
Red lead on right terminal. No reading with black on left terminal. Reads 594 with black on center terminal.


HFA50PA60C: Red lead on left terminal. Reads 437 with black on center terminal. No reading with black on right terminal.

Red lead on center terminal. No reading with black on right or left terminal
Red lead on left terminal. Reads 437 with black lead on center terminal. No reading with black on right terminal

You don't repair things by randomly passively testing components, you need to fault find - to do which you really need to have a circuit diagram, or at least a vague representation of one. If it's not available, as seems likely, then it's a good idea to draw it out, even if you only draw the specific sections that you suspect.

An issue here of course is that the device is self powered, and you need to replicate that - even perhaps spinning it via another motor and a drive belt? (or get a friend to spin it while you measure voltages).

First obvious thing to do (if you've not done it already) is to see if it's actually creating power when you spin it.

Nigel Goodwin said:

You don't repair things by randomly passively testing components, you need to fault find - to do which you really need to have a circuit diagram, or at least a vague representation of one. If it's not available, as seems likely, then it's a good idea to draw it out, even if you only draw the specific sections that you suspect.

An issue here of course is that the device is self powered, and you need to replicate that - even perhaps spinning it via another motor and a drive belt? (or get a friend to spin it while you measure voltages).

First obvious thing to do (if you've not done it already) is to see if it's actually creating power when you spin it.

Click to expand...

Understood, there's no available diagrams. I can post a diagram what rudimentary connections I've identified. These are components that appear to be in the circuit of the power input from the generator and the output to the brake. It's one of those circuit boards that has the connections sandwiched between layers of the composite so it's difficult if not impossible to trace many of the connections on the board.

Yes, the generator is creating power, thought I mentioned that in an earlier post, apologies if I have not.

DRJP said:

OK, I've tested the diodes (removed them first) next to the blue capacitor; they're all fine. Checked the black thermistor, it's working fine.

Click to expand...

What I was suggesting previously was to see if the generator did actually charge the big cap up - quickly - with no other power source connected??

It's possible for a generator to show voltage on a meter but be unable to provide any useful current.

rjenkinsgb said:

What I was suggesting previously was to see if the generator did actually charge the big cap up - quickly - with no other power source connected??

It's possible for a generator to show voltage on a meter but be unable to provide any useful current.

Click to expand...

I'm not sure how to check that. Can you advise? Keep in mind I'm a complete novice at this. Transistors were just becoming a thing when I took electronics back in high school.

DRJP said:

Right, I did check the diodes already and they're fine. How do I check the transistors. There's a ton of youtube videos but I'm not sure what type of transistors these are MOSFET, PNP, NPN...it's all greek to me. Can anyone recommend a video that walks a noob through testing the transistor numbers I listed above?
Or...maybe someone can interpret the results for me:

Multimeter in diode test mode

IRFP360: RED lead on left terminal. No reading with Black lead on center or right terminal
Red lead on center terminal. No reading with black on left or right terminals
Red lead on right terminal. No reading with black on left terminal. Reads 594 with black on center terminal.


HFA50PA60C: Red lead on left terminal. Reads 437 with black on center terminal. No reading with black on right terminal.

Red lead on center terminal. No reading with black on right or left terminal
Red lead on left terminal. Reads 437 with black lead on center terminal. No reading with black on right terminal

Click to expand...

Put black on centre, and Red on Right or LEFT should read the same as Left = 437 +/-10

Diode Test mode is constant low current reading voltage in mV , maybe 2000 full scale.

HFA is just a dual diode with common CATHODE = (-ve) = centre pin 2 so Black always goes to -ve
437 means 437 mV with diode test mode at very low constant current , blank means high impedance overscale or no reading in reverse bias mode.

But the FET cannot be tested alone with DMM. YOu need a bigger voltage to switch the gate on like a 9V battery.

with +9V on G and -ve to S
use diode tester from D (red) to S (blk) ( open circuit) or a short circuit is failure
but 9V on Gate to Source the D to S acts like an ideal diode 000 or 0V.

Tony Stewart said:

Put black on centre, and Red on Right or LEFT should read the same as Left = 437 +/-10
View attachment 143331
Diode Test mode is constant low current reading voltage in mV , maybe 2000 full scale.

HFA is just a dual diode with common CATHODE = (-ve) = centre pin 2 so Black always goes to -ve
437 means 437 mV with diode test mode at very low constant current , blank means high impedance overscale or no reading in reverse bias mode.

But the FET cannot be tested alone with DMM. YOu need a bigger voltage to switch the gate on like a 9V battery.

with +9V on G and -ve to S
use diode tester from D (red) to S (blk) ( open circuit) or a short circuit is failure
but 9V on Gate to Source the D to S acts like an ideal diode 000 or 0V.

Click to expand...

The HFA is reading 420 for both the red on left and red on right with black on center.
That means it's OK, correct?

I'm not sure what you mean by FET. Is that the IRFP360?

See attached for my best attempt to draw out the circuit. The ? surrounded by a circle indicates I can't quite follow where the circuit leads next. I'm also not sure what the component is between the blue capacitor and the IRF 744 but have the markings on it written down. Also didn't label the resistors connected to the blue cap and the thermistor.

rjenkinsgb, I did check and confirmed that there is voltage going to the big blue capacitor when the unit is spinning (while not connected to an external power source. Difficult to get an accurate reading on the voltage, but it's there.​

OK, did a little further testing:

Right of drawing where Tony labeled both "gnd?" and "Gnd" does have continuity with ground.

Top of drawing where Tony labeled "V+ = brake", the G terminal of IFRP360 goes through a "small circuit" (see pix of board below); I don't know exactly what to call it. There is continuity from one end of this "small circuit" to the other with resistance (if that makes sense). I cannot tell where the "small circuit" connects on the other end (other end from where it connects to the G terminal of IRFP360.)

This is the "small circuit":






None of the terminals of IRF 744 are continuous with ground. As Tony has labeled the leads to IRF 744 as G D and S:

G has no continuity with Ground or either of the brake terminals
D has continuity with no resistance to - brake output terminal
S has continuity with 494 ohms of resistance to negative brake output terminal

What's my next step?

Should I take IRF 744 off the board and test it and if so, how do I test it?


I'm still not clear on how to test the IRFP360. I don't quite understand:
"But the FET cannot be tested alone with DMM. YOu need a bigger voltage to switch the gate on like a 9V battery.
with +9V on G and -ve to S
use diode tester from D (red) to S (blk) ( open circuit) or a short circuit is failure
but 9V on Gate to Source the D to S acts like an ideal diode 000 or 0V."

I'm not sure what leads to place the 9v + and - and where to take the diode mode readings once I've applied that power. I also don't know which leads are G, S and D. Recall that I'm a total noob.

OK, my duh, forgot the that leads are labeled on the diagram. Will check it out, thanks.

OK, so I put the + from the 9v battery to the G terminal and the - from the battery to the S terminal on the IFRP360.

I put the DMM on diode setting, put the red probe on the D and the black probe on the S and got 000 with the beeping sound. With the 9v leads removed it shows 000 and beeps. If I then ground the 3 leads together and put the DMM red to D and black to S it shows 1 with no beeping sound.

Not sure how to interpret this. Is this transistor good or should I replace it?

Just borrowed a capacitor -measurement capable DMM, measured large blue capacitor: rated 580 uF, measured on meter as 475 uF. Is this acceptable or should I replace it? I seem to recall a +/- 10% guideline.

OK, can someone explain this?

I removed and tested the IRF 744 and it tested out fine. I also removed another large capacitor and checked it, and it checked out fine.
Then I replaced the components back on to the board:
2 Capacitors and 3 transistors
...and now I'm getting voltage to the brake. It *seems* to be increasing the voltage to the brake when I call for higher resistance on the display panel, but I'm not 100% sure of that. I'll have someone else see if they notice an increased resistance because mine might be wishful thinking.

So, two questions:
1) Bad connection that I inadvertently repaired when removing and reinstalling components?
2) Would it be reasonable to assume one of the components I removed for testing then reinstalled is faulty? I don't mind replacing all of them, the cost would be inexpensive.

Other thoughts?

It could be either - a tarnished connection, or an internal fault in a component that has been (probably temporarily) fixed by the heat of soldering.