Reebok GT40s Treadmill power supply issue?

[notallbad]

Quite sure its the power board at fault.
The treadmill does not power up, the LCD display flashes on and off, almost as though the power supply is cycling on and off.
Getting around 290v steady on the main filter cap though takes a few seconds to creep up to that reading.
Voltage reads about 8v on the rail to the display/control panel but keeps dropping (fluctuating around 6-8v), pretty sure this is not enough to drive the lcd /control panel but could be the power supply shutting down before the volts can get high enough.

The power supply board and components look ok on inspection.

There is an LED on the PS bd but it does not light up or flash - this I believe is used for troubleshooting.

Would greatly appreciate any guidance.

[notallbad]

20170504_105111.jpg

[notallbad]

20170504_105014.jpg

[budm]

"Getting around 290v steady on the main filter cap though takes a few seconds to creep up to that reading"?
Your incoming AC is 230VAC so the DCV between the two legs of the main filter cap should be around 325VDC. So verify that your meter is OK, the incoming AC is OK, and the main filter cap is OK.

[notallbad]

Found a shorted schokty diode SS310 (DD3), located under the cap immediately next to the transformer.

What alternative can I use temporarily just to see if it gets it working?

[notallbad]

20170503_212718.jpg
20170503_212657.jpgThanks Budm
Shall check main filter cap and get back to you, it does read around 450uF in-circuit using a cap meter.
240v def coming into board across AC1 and AC2 via IEC kettle lead, 8A fuse, rocker switch, EMI filter, transformer.

[notallbad]

Powered back up with one leg of the faulty DD3 diode legs 'lifted' and it powers up fine. Lcd lit but beeping an error, understandable as ancillaries disconnected i.e incline motor and incline sensor, treadmill drive motor.

Really need to find an alternative diode!

[jetadm123]

ss310 is a 100v 3A schottky diode made by several companies under different part numbers.

[notallbad]

Would a 1N5401 suffice?
Somewhat larger in physical size but there is adequate space to fit it in.

[japlytic]

Originally Posted by notallbad

Would a 1N5401 suffice?
Somewhat larger in physical size but there is adequate space to fit it in.

For this application, you would need a Schottky unit given its use at the output of a switching power supply.
What are the brands on the electrolytic capacitors on this board?

[stj]

here you go,
3 different sizes to choose.
http://uk.rs-online.com/web/p/rectif...iodes/9179219/
http://uk.rs-online.com/web/p/rectif...iodes/9179209/
http://uk.rs-online.com/web/p/rectif...iodes/9179164/

so what is the EXACT length & width of the original?

[notallbad]

Originally Posted by japlytic

For this application, you would need a Schottky unit given its use at the output of a switching power supply.
What are the brands on the electrolytic capacitors on this board?

Caps are Nicon.

Fitted a 1N5401 and it seems to all be working.

Shall replace with a Schottky over the next few days before it gets used too much!

[notallbad]

Originally Posted by stj

here you go,
3 different sizes to choose.
http://uk.rs-online.com/web/p/rectif...iodes/9179219/
http://uk.rs-online.com/web/p/rectif...iodes/9179209/
http://uk.rs-online.com/web/p/rectif...iodes/9179164/

so what is the EXACT length & width of the original?

The SS310 is 4mm long x 2mm wide.

Thanks shall take a look at those equivalents above.

[notallbad]

Just to confirm, all caps are Nicon branded with the exception of the filter cap which is UUcap branded.

Whilst it has been working with the temporary diode I have now replaced it with a Schottky SK310A. Still prefer the 9 pence fix but paid £2.64 for 5 rather than £1.64 just for one so do have spares if ever needed in the future.

Will update on the performance but it is working still!

[notallbad]

My partner informs me that there is a high pitched 'buzzing' coming from the power supply. Not something I heard but being somewhat older than her that probably makes sense.
I can confirm that there is an oscillating 'buzz' coming from the diode/ transformer/cap area, can't quite narrow it down exactly.

So, I put the 1N5401 back and although it is 'buzzing/humming' it is only just very audible with my ear very very close to the unit which is probably a tolerable/allowable/acceptable amount.

Now, what could be the cause? The diodes have specs near enough identical from what I can see with the exception that the 1N5401 is not a Schottky fast acting. Could it be the capacitance (Cj)?
1N5401 30pF
SK310A 250pF
SS310 190pF

Photo shows a comparison between the three for reference.

[notallbad]

Or possibly the Ifsm (Peak forward surge current) rating?

[notallbad]

Might also be worth mentioning that manufacturer specs seem to differ.
Multicomp Ifsm 100A
MIC Ifsm 80A
What the hell??? Surely if the part is an SS310 the specs should be the same regardless of manufacturer.
Or is it the way in which the specs are presented, peak forward surge current different to forward surge current perhaps?

[aneng]

Hi. I have the exact same treadmill with the exact same fault ! (Well, the symptoms are the same - instead of powering up, it pulses about twice a second, as if the PSU is cycling).

Have you got any further with yours ? I'm going to take a look at the diode you mentioned on mine.

[notallbad]

Doubt it will be the same diode causing your fault, with the diode completely removed it still powers on albeit with the error code.

Remove the power/control board and inspect for obvious signs of damage etc... If nothing visibly wrong begin
on-board testing of the diodes, resistors etc

I can confirm results if anything looks untoward by comparing results before you start removing/replacing components.( Obviously some components give slightly differing results on-board than off, they may also differ from my results but at least be of some help).

I have put the 'temp' diode back for now as its working and partner can continue using it.

Keep us/me informed of any developments.

Also confirm that your board is the same as mine and whether the led on the power/control board is lit or not or flashing.

[aneng]

I haven't had a chance to look at it again yet, but you mention on-board testing of diodes & resistors... How does that work ? How can I test a diode, for example, without lifting one leg ? Likewise, resistors aren't going to read their actual values if they are in a circuit are they ?