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 SOLVED **Hallicrafters SX-71 meter help

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stareagle

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Join date : 2012-12-17

PostSubject: SOLVED **Hallicrafters SX-71 meter help   2012-12-17, 8:44 pm

Greetings!; I am restoring this receiver and have it working pretty good. I am having a problem with the "S" meter. The meter is good and it is a 5ma meter (OEM), The voltage to the meter seems to be OK. But I can only get 0-2.1 ma when adjusting the pot. It is connected to a 6au6. The pot seems OK (500 ohm). Not really sure what I should be looking for as I am dealing with Amperage, not Voltage etc.. Can someone put me on the right track? I should have all the equipment needed. Just not sure how to proceed. Embarassed Embarassed Thanks in advance!
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Cliff Jones
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Join date : 2010-11-22

PostSubject: Re: SOLVED **Hallicrafters SX-71 meter help   2012-12-18, 2:02 am

This is from the manual
S meter adjustments

mechanical adjustment-

Turn the receiver off. Directly below the S-meter on the front panel is a round metal medallion which is pivoted at the bottom so that it may be rotated to one side to provide access to the meter adjustment screw. Carefully rotate this adjustment screw until the pointer is in line with the right hand index mark on the "S" meter.


----------------------------

If this doesn't work then you are going to have to investigate the following parts first, then voltages.

Before plugging in the set do the following check to make sure the values are correct.
C10A cap 4000mmf from ground may be defective and reducing voltage.
R9 330,000 ohms
R42 should be 3,300 ohms
and c108 4000mmf
R43 ("S" meter adjust) can be either 200 ohms or 500 ohms
R 44 82 ohms 1/2 watt yellow lead from meter




For voltage checks set front panel control to the following:
Electrical adjustment-

1. Short the antenna terminals to the chassis
2. Set the receive/standby switch at, RECEIVE, B.F.O. switch at OFF, SENSITIVITY control fully clockwise and the NOISE LIMITER switch at OFF.
3. Turn the receiver on.
4. The electrical adjustment control for the "S" meter is located on the rear apron of the chassis, Slowly rotate this control until the "S" meter pointer indicates zero.
BFO off
Reception normal I.F.
Noise limiter on
Main tuning - low freq end of dial
Band-spread - low freq end of dial
Band selector band 1
tone CCW
Volume CCW (switch on)
Receive/ Standby Receive
Sensitivity CW


Check for the following voltages.


V2 (6AU6-1st Converter)
Measured between socket terminals and ground with zero signal input
(K) cathode 5v
(SG) suppressor grid 75v
(P) plate 250v
(G) (PIN 6)Grid -12 (or 0v varies depending on setting of main tuning gang and switch)


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stareagle

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Join date : 2012-12-17

PostSubject: Re: SOLVED **Hallicrafters SX-71 meter help   2012-12-18, 7:43 pm

Thanks for the quick responce Cliff ! But it will have to wait now. I gave myself a "self inflicted problem". While probing the 6au6 I smoked something. I think it was C 9 or R 15 (Sams Photofact) . Now I have to fix that first as I have no sound now. Audio circuit is fine. Its the front end. I must remember to wear my magnafying glasses. Your suggestions look good. I will let you know in a day or two. santa
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stareagle

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Join date : 2012-12-17

PostSubject: Re: SOLVED **Hallicrafters SX-71 meter help   2012-12-21, 4:34 pm

Hi everyone, Well I fixed the damage I caused in the front end and started with the procedures outlined by CLIFF JONES. Yup, C-10 was leaking. It is two ceramic disk caps in one. I installed two sprague X5E .004, 1000v disk caps to replace the 2 in one cap. The reading is 0 - to well over 10ma now.. Thank you Cliff, bounce bounce BTW, Sams is slightly different than Ryder and Hallicrafters service manuals. C10 was a different cap on the Sams Rolling Eyes
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Cliff Jones
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Join date : 2010-11-22

PostSubject: Re: SOLVED **Hallicrafters SX-71 meter help   2012-12-21, 5:57 pm

I marked this as solved. I'm very pleased that its now working!

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