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Roaster resurrection project
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Ian
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Ian
Joined: 21 Jan 2003
Posts: 1,449
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.



Cheers

Ian

 
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PJK
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PJK
Joined: 21 Jan 2002
Posts: 2,314
Location: Shingle Springs CA
Expertise: I love coffee

Espresso: Rancillo Silvia, Tonic...
Grinder: Modified Rocky, Elma side...
Vac Pot: Old Silex
Drip: Melitta BCM 4  +Some old...
Roaster: Hottop, Modified Z&D,...
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.



Cheers

Ian

Posted June 9, 2012 link


 
Philip J. Keleshian
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Ian
Moderator
Ian
Joined: 21 Jan 2003
Posts: 1,449
Location: England

Espresso: Euro2000,Rancilio
Grinder: Mazzer,La Cimbali
Vac Pot: Cona-->CraigA
Drip: Belgique for emergencies
Roaster: Primas with variac
Posted Mon Jun 11, 2012, 2:04am
Subject: Re: Roaster resurrection project
 

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?

http://www.maplin.co.uk/thermal-fuses-470


Cheers

Ian

 
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Ian
Moderator
Ian
Joined: 21 Jan 2003
Posts: 1,449
Location: England

Espresso: Euro2000,Rancilio
Grinder: Mazzer,La Cimbali
Vac Pot: Cona-->CraigA
Drip: Belgique for emergencies
Roaster: Primas with variac
Posted Tue Jun 12, 2012, 7:30am
Subject: Re: Roaster resurrection project
 

Had a spare half hour yesterday:

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.

(Photostream updated)


Ian

 
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Ian
Moderator
Ian
Joined: 21 Jan 2003
Posts: 1,449
Location: England

Espresso: Euro2000,Rancilio
Grinder: Mazzer,La Cimbali
Vac Pot: Cona-->CraigA
Drip: Belgique for emergencies
Roaster: Primas with variac
Posted Tue Jun 19, 2012, 9:15am
Subject: Re: Roaster resurrection project
 

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.


Cheers

Ian

 
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