[Boatanchors] Johnson Ranger Fuses

[Bill Stewart]

Tnx everyone for the info on fuses in the Ranger. 
Rodger, tnx to you for, also, answering my 'why?' 
Makes sense now that I know more about the reasoning. 
73 de Bill K4JYS 

From: "Rodger Singley" <wq9nsc at live.com> 
To: "cwopr" <cwopr at embarqmail.com>, "boatanchors" <boatanchors at mailman.qth.net> 
Sent: Friday, November 23, 2018 2:51:32 PM 
Subject: RE: Johnson Ranger Fuses 



Bill, 



The two fuses were used because the MDL is a “slow blow” or time delay type fuse that will carry in excess of its 3A rating for a short period of time before it opens. The 5 amp MTH fuse is a regular “fast blow” fuse and will open pretty quickly once its 5 amp rating is exceeded. Note that both types will carry a bit more than their nominal rating so for those who want to measure into the tens of mils look at the spec sheet. 



The reason Johnson chose two different fuses was they did not want the rig drawing sustained current of more than 3 amps or greater short term peaks than slightly over 5 amps. In theory the 5 amp will open quickly with a serious failure while the 3 amp will open when someone is running sustained power well in excess of what the Ranger was intended to develop. These fuses were also chosen with respect to withstanding expected inrush current. 



I would use an inrush limiter and a single fast blow 3 or 4 amp fuse; if you are prone to tuning mistakes the 4 amp will be less troublesome. 



Rodger WQ9E 



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Mail ] for Windows 10 



From: boatanchors-bounces at mailman.qth.net <boatanchors-bounces at mailman.qth.net> on behalf of Bill Stewart <cwopr at embarqmail.com> 
Sent: Friday, November 23, 2018 11:01:00 AM 
To: boatanchors 
Subject: [Boatanchors] Johnson Ranger Fuses 
I recently acquired a Ranger and have been looking around inside and find 
that a PO added a 3 wire plug, but NO fuses. It originally had the fuses in the 
line cord. Now looking for a place to put a couple of fuse blocks. I notice that 
the parts list calls for different value fuses in each leg of the ac to the pwr xfmr. 
Why? Can a compromise be safely made as to the fuse values. The dates are 
late 1954 on schem. and parts list. Tnx.... 
73 de Bill K4JYS 

FYI: F1 - 3A 125vac MDL Fusetron 
F2 - 5A 250vac MTH Fuse 
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