Alternator Diode - Need Help with Part Number

#1 10-13-02, 08:47 PM

Hi All,

I fly a 1975 337G Normally aspirated. THe front alternator was giving me trouble and after going through the troubleshooting process we found that the power diode (the one sitting on the front firewall that connects directly to the alternators output is bad. I have the parts manual and it does not make reference to this part. Does anyone know what this part # is and where to get it. It is a 70 amp power diode that sits inside a heat sink.

Any help is appreciated.

Thanks,

Chris

Guy Paris · #2 10-13-02, 09:39 PM

Chris, I had a like problem in 1996, The part came from an electrical supply house. The mech. I dealt back then cross referenced it to this. (item no. SK7268) (item description SK7268/6068) it was $16.95 plus tax. Some where I recall seeing a part number in a parts manual for that diode. maybe some one might have it. Guy.... old72driver....

#3 10-14-02, 07:33 AM

Thanks for the quick feedback.
mathylop

GMAs · #4 10-14-02, 12:59 PM

We went into great lengths about he changing and testing of the diodes on the firewall... I think I may have the old article on the computer at home... as it has the complete thing... might be kinda nice to have them archived so that others that have the same question might be able to get to the web site and go to the page directly...

As I recall they are 200 piv 80 amp diodes... but, we are suggesting that you put a 400 piv 85 amp one in... you can get them thru radio shack or some other electronic parts store... as well as ECG and motorola... but, they diodes have to be put in with silicon lube... as well as heat sinked well... so that they will have a good life... and the cost is actually cheeper than trying to stay with the old 70 amp ones..

I will look up the article again if you need it... maybe skyking has a copy of it too so he could put it on for you also.. G.M> GMAs

Ed Coffman · #5 10-14-02, 01:34 PM

The part number on the diodes we use is 85HF20. Can't remember but I think we ordered them from Newark Electronics.
www.newark.com.

Ed Coffman
________
Portable vaporizer reviews

#6 10-14-02, 08:51 PM

Once again, thanks to the awesome help from you fellows the problem is solved. I went with Guy's solution (primarily because this part was immediately available). The part that we installed was ECG6068 which is a R-800 PRV, 70 A, Cathode Case Diode. I paid $19.95 and had it installed a few hours later (yes, with heat synch gel)

I would have gone with GMAS's supped up version of this diode but would have to wait a few days. Either way, once it was installed our bus voltage was a beautiful 28 volts from either the front or the rear.

Thanks again....If anyone ever needs advise troubleshooting the electrical system on their skymaster please don't hesitate to email me at chris@mediajelly.com. I've been over it a thousand times and have it down real good!

Thanks again to all!

Chris

GMAs · #7 10-15-02, 12:44 AM

Sorry to say you put the same ones back in that they were original... cessna went to the 85 amp ones some time ago.. because the others were not taking the spikes... but then again if you have had them out once.. twice is not so hard .. smile... G.M> GMAs

GMAs · #8 10-15-02, 12:48 AM

Cheeper too... cost 11 bucks each... but, some places you can get them for 6 bucks each... as the 85's are more common... next step up is the 100 amps ones... but, 85's seems to be taking the shock Ok... otherwise the origianls were shockley types.. regular ones won't take the surg when the gear pump comes on... or the flap motor tries to zero the voltage and the diodes have to go through a sort of water hammer but, electrical in nature... G.M> GMAs