Ampeg PF350 not working - any ideas?

MattBanshee

My Ampeg PF350 head, which has worked fine up til now, has suddenly decided to not work. It hasn't been used for about 6 weeks but has been kept safe since. When plugged in and switched on, the pilot light in the translucent power switch on the back comes on, but the front panel doesn't light up at all (not even the fault light) and no sound output. Any ideas on what it might be? Thanks!

ICBM

Sounds like it may have blown an internal fuse, and/or part of the power supply - the two will most likely be related. Switch-mode power supplies are usually not easy to repair. These amps do not have a good reputation for reliability (though the PF500 and 800 don't seem to be as bad), and Ampeg are less than helpful with schematics. I had a dead one of these in recently with a similar fault and the only viable fix I could find was to advise the owner to buy a PF500 that was going for a good price locally...

DJH83004

As IC says there is an internal fuse on the power supply board, which is the most likely culprit, unfortunately it has a switch mode power and Class D digital amp which makes for a difficult repair (certainly by me!) so usually a return to the manufacturer for a board swap I'm afraid. 

jpfamps

I've not had much success repairing these either to be honest; nor have I had much technical support either from Ampeg, although this may change now Ampeg are owned by Yamaha.

MattBanshee

Whilst googling the issue, I came across this:

https://www.talkbass.com/threads/ampeg-pf-500-fuse-problem.927210/

Is this worth having a go at?

ICBM

MattBanshee said:

Whilst googling the issue, I came across this:

https://www.talkbass.com/threads/ampeg-pf-500-fuse-problem.927210/

Is this worth having a go at?

It's worth having a look - if the fuse has blown, it could be just because there was a tiny bit of condensation in it or something, after being unused for a while. If so, change the fuse and try it again - if it blows again then there is something more seriously wrong.

jpfamps said:

I've not had much success repairing these either to be honest; nor have I had much technical support either from Ampeg, although this may change now Ampeg are owned by Yamaha.

I hope so! I've always found Yamaha pretty helpful.

MattBanshee

Does this look like the right replacement fuse?

10 Amp T10AH 250V 20mm x 5mm Ceramic Fuse x 2 by electrosmart® https://www.amazon.co.uk/dp/B004Z0NNFK/ref=cm_sw_r_cp_apa_FsTABbDB85514

Edit: Or is this better?
https://m.ebay.co.uk/itm/5-CERAMIC-SLOW-BLOW-FUSES-10A-10AMP-T10AH-20-x-5mm-250V-/121585109684

ICBM

Not for the PF350 - it takes a T6.3AL fuse not T10AH.

The one in the dead one I still have here is a clear glass fuse, not ceramic - it shouldn't make any difference for this application though.

MattBanshee

Thanks for the info ICBM. Is it still a 5x20mm?
Edit: these? 
 https://www.amazon.co.uk/dp/B01MSDFXJX/ref=cm_sw_r_cp_apa_U6TABb1EED524

Also, I haven't taken it apart yet; is it fairly obvious where this fuse is located?

ICBM

MattBanshee said:

Thanks for the info ICBM. Is it still a 5x20mm?
Edit: these? 
 https://www.amazon.co.uk/dp/B01MSDFXJX/ref=cm_sw_r_cp_apa_U6TABb1EED524

Yes, although you don't need 10 really .

MattBanshee said:

Also, I haven't taken it apart yet; is it fairly obvious where this fuse is located?

Yes, it's in the corner near the power socket.

I've also just checked that the illuminated switch comes on even if the fuse is blown - it does.

MattBanshee

ICBM said:

MattBanshee said:

Thanks for the info ICBM. Is it still a 5x20mm?
Edit: these? 
 https://www.amazon.co.uk/dp/B01MSDFXJX/ref=cm_sw_r_cp_apa_U6TABb1EED524

Yes, although you don't need 10 really .

MattBanshee said:

Also, I haven't taken it apart yet; is it fairly obvious where this fuse is located?

Yes, it's in the corner near the power socket.

I've also just checked that the illuminated switch comes on even if the fuse is blown - it does.

Great, thanks. I'll try changing the fuse and will keep my fingers crossed.

MattBanshee

Update:

Opened it up to check the fuse. Fuse is fine. 
Noticed this:
https://i.imgur.com/0qlkSft.jpg

Pushed back on, now powers up!

Bridgehouse

MattBanshee said:

Update:

Opened it up to check the fuse. Fuse is fine. 
Noticed this:
https://i.imgur.com/0qlkSft.jpg

Pushed back on, now powers up!

Awesome! Easy fix then

ICBM

Result! If only they were all that simple...

It may be worth putting a small amount of hot-melt glue or silicone on the connector to stop it coming off again.