Chris -
OK, I assumed you were measuring the 5V on the DR-7 board. It has two of it's own 5V regulators to
drive the logic chips. If you have a 2M HT, you can stick a wire in the CNTR jack on the rear
panel, switch to EXT on the switch above the jack, and see if you can count the HT frequency. You
can also do this with a piece of wire brought near a lowband transmitter loaded into a dummy load,
or ... This will verify the counter operation.
If you are measuring the 5V supply to the Parent Board, there are electrolytics all over the various
cards, and the 5V goes to just about all of them. You may have to pull cards one at a time (POWER
OFF) to determine which one is pulling the 5V line down. An ESR meter will simplify this task. If
you have a DMM with a good low voltage range, you can also measure the 5V bus at each card socket
looking for small differences to hint which card it may be. There's also the possibility that there
is more than one! :-) All these caps are well past their life expectancy at 40 years old! Also
check the +24V line and the -5V line. The -5V line will only read about -3.5, but this is OK.
Also check the +10R and +10T lines to make sure they are switching properly. Unlocked VCOs usually
present as rapidly changing frequencies settling at ~ 17 MHz for 20M and down, and ~ 32 MHz on 15M
and up.
Do you have a Service Manual?
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Chris Hughes wrote:
Morning Garey
I suspect the receiver , no signals detected ,
audio amp working fine though , ok on the leaking caps , I removed the
power supply board and tested the caps 2112,2104 2103 , they seemed ok
so I stopped there , ?
----- Original Message ----- From: "Garey Barrell" <[email protected]>
To: "Chris Hughes" <[email protected]>
Cc: <[email protected]>
Sent: Tuesday, March 23, 2010 6:51 AM
Subject: Re: [Drakelist] Drakelist Digest, Vol 21, Issue 29
Chris -
First step is to determine if the problem is the receiver or the
counter.
Are you able to tune in a signal on the receiver?
4.67V is too low on the 5V line. It should be less than 0.2V more or
less than 5.00 V. Possibly leaky electrolytic caps.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Chris Hughes wrote:
Hi all
Before I start pulling things apart ..my TR7 counter
display has locked up accept for the last 2 numbers which are
rapidly changing and not responding to any controls , the 10 volt
line is spot on but I can only get 4.67 volts on th 5 volt line ?
this radio was locked up in storage for 20 years but its been
working well up untill a couple of months ago any idears ....Chris
ZL2UKT
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