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Gaggia Coffee mods resulting in temperature drop < 2 deg C
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Discussions > Espresso > Espresso Mods > Gaggia Coffee...  
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witoldb
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Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

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Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:04pm
Subject: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

I bought neglected Gaggia Coffee for $30 and implemented some mods to improve its temperature stability.
After mods, maximum temperature drop is between 1.4 and 1.6 deg C at the end of double shot.
The same mods can be applied to Classic as well.
Modifications include:
  1. Internal RTD probe in place of brew thermoswitch.
  2. REX-C100 PID modified from relay to voltage outputs (with alarm function for steaming); with RTD resolution is 0.1 deg C
  3. SSR activated by PID output, PID alarm or preheat circuit
  4. Passive preheat coil; 6 turns of 1/4" tube (approx 30ml volume)
  5. Insulation washers between group and case
  6. Melamine foam insulation for boiler sides and top
  7. Circuit to add between 20 and 40% power to heaters when pump is activated (adjustable with pot)

I didn't have to adjust the safety valve - I've measured 12.5 bar on the pump discharge and around 8.9 to 9.0 bar after group valve (with flow throttled down to 75ml in 30 sec).
My PID settings with 0 to 200 deg C input range are: P=12.8    I=40    D=2.  These are different from autotune values for better control during the shot.

Coil + 6mm RTD (PT100) probe photo.
Compression fitting installed in place of brew thermoswitch (drilled and taped to 1/8" BSP).
End of probe is midway between boiler internal wall and outlet/raiser tube.

witoldb: coil+RTD probe.JPG
(Click for larger image)
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:11pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Priming valve plugged off by soldering.
Leaking steam valve repaired by filing off rolled edge, polishing the stem end and o-ring change.
I've cut  M12x1 external thread and installed stopper nut - valve can be repaired now any time.

witoldb: stm valve nut + plug + coil.JPG
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:14pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Melamine foam insulation with aluminium sheeting and self locking SS bands.

witoldb: insulation.JPG
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:17pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Steam wand tip was missing - made extra long one for ease of cleaning.
Thread is ordinary coarse M6 (remaining wall = 0.5mm).

witoldb: steam wand tip.JPG
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:19pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Complete wand assembly. It is single 1mm hole.
Later I've added piece of silicone tube over 1st bend.

witoldb: steam wand assembly.JPG
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:23pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

PID modification details.
OUT and ALM1 relays removed, 4 jumper wires and 2 x signal diodes installed (1N4148 or similar).
Take care not to bend wires joining the boards too much/many times - they are not too flexible and will break.

witoldb: PID mods.JPG
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:29pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Above mods will convert outputs to voltage type as marked on the photo.
I've used 2nd Alarm terminal to connect low voltage ground signal (white wire on previous photo).
I'm using it for preheating circuit (will post the details later after finishing wiring diagram).

witoldb: PID terminals.JPG
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SJM
Senior Member


Joined: 17 Nov 2004
Posts: 1,719
Location: CA
Expertise: I love coffee

Espresso: SAMA (2), Maximatic, Cremina...
Grinder: K-10PB, Rancilio MD-50
Vac Pot: no like
Drip: no like
Roaster: HotTop   Huky en route
Posted Tue Apr 1, 2014, 12:30pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Nice work !!!!
I hope you will bring this information over to the Gaggia Users Group as well.
Otherwise I can post a link to here, but it would be nicer if you posted it yourself :-)))

Susan
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:32pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Above PID mods are applicable to cheap models from China

witoldb: PID label.JPG
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witoldb
Senior Member


Joined: 15 Aug 2013
Posts: 111
Location: Dubai UAE
Expertise: I like coffee

Espresso: Sanremo Treviso LX,...
Grinder: Vario,Elektra MXS,...
Roaster: DIY 250g drum roaster
Posted Tue Apr 1, 2014, 12:32pm
Subject: Re: Gaggia Coffee mods resulting in temperature drop < 2 deg C
 

Front view of controller I've used

witoldb: PID face.JPG
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