# Curtis 1204 Upgrade Questions



## sonicj (Mar 17, 2010)

well... i went ahead and ordered 15 - IRF3710. why 15? not totally sure! sanded and polished all mating surfaces. desoldering wasn't too bad... i used a $11 desoldering iron from radio shack (d***, $8.59 on sale!). i think i removed the transistors first, then evacuated the holes. installed the new transistors, found some 75Ω resistors, and installed the 2 missing capacitors. almost there! (i think!)

still uncertain what to do with the missing diodes... are they even needed for a series motor? 

not too clear on the gate resistors? is the stock 75Ω value still appropriate?

also not sure if i should go ahead and populate the remaining transistor positions??? i was concerned about the missing diodes so i was only going to use 12, but whats the point of upgrading if im leaving the thing 1/4 empty? right? cheers!
-sj


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## sonicj (Mar 17, 2010)

i'll post some pics of the mostly completed board in a bit!


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## gaminde (Sep 18, 2011)

Sonic did this work

Gaminde


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## sonicj (Mar 17, 2010)

yo! whaddup LG!

i haven't tried it yet... i just received some 75Ω resistors from newark the other day but haven't stuck them in yet. 

still unsure about populating the missing diodes and the value of the gate resistors... :confused 
-sj


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## gaminde (Sep 18, 2011)

Well what are you waiting for, do you have a variable power supply, and maybe a 200 watt light bulb for testing. Start with a low voltage and work your way up.


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## sonicj (Mar 17, 2010)

just been busy lately with other projects... ADD i suppose. i've got a 500A Alltrax in the cart so its not pressing. 

i have a HP variable DC supply 0-120V but its only good for 0.5A. i was thinking i could bypass the relay in my old charger and use that as a supply or just wire it up to the traction pack in the GC with a proper fuse. i think the lightbulb needs a coil inline for inductance... anywho, i might break out the soldering iron tonight. holla!
-sj


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## jehan12413 (Feb 4, 2010)

When I rebuilt some curtis 1205 and 1204 controllers I used IRF 3710 and filled every available spot. As far as the gate resistors I have used 100 ohm when I ran out of 75 and it seemed to work just fine. I operated these units from 36V to 66V. If I recall correctly the diode I used to fill the extra positions was a MUR2020.


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## gaminde (Sep 18, 2011)

That's great Now I have to start a notebook somewhere. I do have 1 question on whether there is software In the controller that controls total current Or is it only limited by the number of transistors


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## gaminde (Sep 18, 2011)

Sonicj what were the original transistors in your unit?
I just opened up a regen unit 1510 5150 and have numbers like 
IR334H which i cannot find, and 94-2355 I can find 2355 but its only 2.5 amps and there is not hundreds of them


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## sonicj (Mar 17, 2010)

jehan12413 said:


> When I rebuilt some curtis 1205 and 1204 controllers I used IRF 3710 and filled every available spot. As far as the gate resistors I have used 100 ohm when I ran out of 75 and it seemed to work just fine. I operated these units from 36V to 66V. If I recall correctly the diode I used to fill the extra positions was a MUR2020.


thanks jehan! USPS delivered 2 x MUR2020 yesterday 



gaminde said:


> Sonicj what were the original transistors in your unit?
> I just opened up a regen unit 1510 5150 and have numbers like
> IR334H which i cannot find, and 94-2355 I can find 2355 but its only 2.5 amps and there is not hundreds of them


RFP40N10 from intersil

apparently, curtis likes to use end of life, esoteric, or otherwise difficult to procure parts. makes production exciting i suppose.
-sj


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## sonicj (Mar 17, 2010)

gaminde said:


> ....94-2355 I can find 2355 but its only 2.5 amps and there is not hundreds of them


94-2355 brings up IRF3710 at avnet via findchips.com. 
-sj


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## jehan12413 (Feb 4, 2010)

Curtis does have a current limit which works by measuring the voltage drop across the MOSFETS. Not the best way to do it but it seems to work ok for low voltage applications. The adjustment is a small trimpot on the control board labeled CL.


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## Dink (Jun 3, 2010)

jehan12413 said:


> When I rebuilt some curtis 1205 and 1204 controllers I used IRF 3710 and filled every available spot. As far as the gate resistors I have used 100 ohm when I ran out of 75 and it seemed to work just fine. I operated these units from 36V to 66V. If I recall correctly the diode I used to fill the extra positions was a MUR2020.


Can you help with curtis controllers? I have 3 Taylor Dunn 62-205-00 controllers(curtis 1205) to test and repair. These differ in that they only have 2 small terminals. What is needed to build a simple basic throttle?


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## DavidP (Jun 9, 2010)

It is an older thread, but for anyone considering upgrading a Curtis 1204/1205, this is a webpage I found years ago ... 
I hope this helps anyone thinking of this upgrade ... 
It has some good information and pictures to give you an idea what is involved ... 






DC motor controller upgrade.


on this page I'll tell you and show via the means of photos of how I did the upgrade of Curtis motor controller, how to open it without damaging,



www.ferromit.com


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