Ian Moderator Joined: 21 Jan 2003 Posts: 1,401 Location: England
Espresso: Euro2000,Rancilio Grinder: Mazzer,La Cimbali Vac Pot: Cona-->CraigA Drip: Belgique for emergencies Roaster: Primas with variac
Posted Sat Jun 9, 2012, 3:59am Subject: Re: Roaster resurrection project
A mate came over on Friday so while we were chatting I thought I would carry on stripping the roaster Flickr
A picture that may be of particular interest is 3930 which shows what is on the other side of the screws that are on the right hand side of the roasting chamber. The top one contains a thermal fuse which is inline with the mains live. The bottom one looks to be a glass encapsulated thermistor.
With the thermal fuse bypassed, the machine powered up (3934). The afterburner, light and all three fans work and that is as far as we got - ran out of time.
Posted Sat Jun 9, 2012, 10:16am Subject: Re: Roaster resurrection project
Hi Ian,
I ended up with a dead Z&D (which I bought for my parts stash) which failed because of one of those fuses near the cat. With a Z&D (now Nesco) you need a parts stash since they won't sell parts.
My guess is that Joe will either sell or give you one or at least tell you what temperature it was so you can get one locally. Do you have Radio Shacks. They have them.
Phil
Ian Said:
A mate came over on Friday so while we were chatting I thought I would carry on stripping the roaster Flickr
A picture that may be of particular interest is 3930 which shows what is on the other side of the screws that are on the right hand side of the roasting chamber. The top one contains a thermal fuse which is inline with the mains live. The bottom one looks to be a glass encapsulated thermistor.
With the thermal fuse bypassed, the machine powered up (3934). The afterburner, light and all three fans work and that is as far as we got - ran out of time.
Hi Phil, I was originally intending to power the heating elements directly from a variac but thinking about it, for 82p, a level of protection is a good idea. Thanks for the suggestion.
I need to go to the electronics shop to get some toggle switches so I'll see what they've got while I'm down there. I think Maplins is our version of Radio Shack?
On bypassing the thermal fuse, the unit powered up but was showing error 2. So assuming the thermistor has also blown and not knowing the spec., I replaced it with various resistors and found that 100K cleared the error. This allowed nearly normal functioning of the machine but obviously without the thermistor there is no temperature control.
All of the individual components seem to be functioning so I'm guessing that the fire was caused by a circuit board fault holding the heater on or something like that?
I ought to say that although the roaster is Chinese made, the quality of manufacture does appear to be fairly good. Certainly better than I was expecting anyway.
While working on the electrics, I had a test patch of Mr Muscle on the door. That was a 30min treatment which worked pretty well so could probably reduce that to 20-25 mins on the rest of it.
I noticed that the door was twisted slightly (about 1/4" out at the top left). If you look at 3952 you can see the scorch marks where the flames had gone round the door seal. It was easy to straighten and might be something worth checking if you're getting poor results.
The next stage will be a general clean up, removal of the electronics and fitting of the switches ready for the re-wiring.
Been rewiring in spare moments here and there - I removed the pcb,switch panels and transformer. New switch plate installed with all the components (except the heater) on separate toggle switches.
The cooling fan, exhaust fan, afterburner and light are on mains voltage with the motor and small fan on 12v DC. The heater elements are connected direct to a variable transformer. The roaster isn't properly assembled yet, the front switch panel is just held on with tape. Flickr album updated.
I did a dry burn first in the workshop to test all the functions and burn off any deposits that I hadn't reached. There was some visible smoke without the afterburner but it was surprisingly effective when switched on - the visible smoke almost disappeared.
First experimental roast: I installed a thermocouple in approximately the same place as the original thermistor but on the other side of the chamber. Also, I had a voltmeter on the variac to monitor heater input voltage.
It was obviously a learning experience with this setup but quite good fun being manually in charge of the roast. It was all over in about 14 minutes mainly because I wasn't quick enough with juggling the variac and various fans. Pic 4100 is the first roast, and to be fair, it looks more even in real life than it does in the pic.
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