REPAIR AND RESTORATION OF THE SR-400
23
WDØGOF 6/22/20014
5-3. OPTIONAL 6 MEG IF ALIGNMENT
The goal in this operation is to produce flat response through the 6 Meg I.F. Some roll of at the ends is expected
but from 3.550 through 3.950 the response should be flat. We will accomplish this task in the transmit mode
using the signals generated within the radio. The expected output level of the 6meg I.F. is 1vpp.
It is important that the bias has been set up to spec (70mills with no drive to the finals). If you are concerned
about the final tubes adjust the bias for an idle current of 30 or 40mills.
1, Remove v12 the heterodyne oscillator tube.
2, Set band switch to 80 meters
3. Connect X10 scope probe to V11A pin 7
4. PRESET the following controls:
RF GAIN MINIMUM
AF GAIN MINIMUM
MIC GAIN MINIMUM
RF LEVEL MINIMUM
RIT switch OFF
RIT control CENTER OF ITS ROTATION.
CAL CENTER OF ITS ROTATION
FUNCTION to USB
5. Turn the OPERATION switch to MOX and allow 20 minutes for warm up.
6. Tune the freq dial to 3.550.
7. Switch the function switch to the TUNE position.
8 Adjust the top and bottom slug of T1 for peak. Then adjust the bottom slug DOWN for a reduction in signal
of about 5%. Then adjust the top slug UP for an equal reduction of signal.
9. Adjust the top and bottom slug of T2 in the same manner as you did T1.
10 Tune the freq dial to 3.950
11. Adjust both slugs in T1 and T2 for peak signal. Record or make note of the peak voltage.
12. Tune the freq dial slowly back to 3.550 while observing the signal on V11A pin 7.
If the signal does not dip or peak more than 0.1v then all is well and you are done. You may have to repeat the
steps 6 through 12 several times to get it to balance at both ends.
5-x. ADDITIONAL TECHNICAL INFORMATION SOURCES:
There is a wealth of technical information on the entire Hallicrafters SR series transceivers available on the
WWW. Here are three of the best.
http://k9axn.com/
: This site belongs to Jim Liles. Jim is the most knowledgeable person I know on the SR-
400 and the SR-2000. If you want to make your 400 a super 400 visit Jim’s site.
http://www.w9wze.net/
: This site, known as the HHI site is an open to all site. When you get to the site scroll
down the left side to
Technical Info
and pick a category. I do not know what the total membership to the
“reflector” is but any post to
hallicrafters@mailman.qth.net
will get almost immediate results.
https://groups.yahoo.com/neo/groups/HallicraftersRadios/info
: This is a member only site. It is free to join
and I strongly recommend joining if you are a Hallicrafters fan. In the files section of this site is the largest
collection of Hallicrafters technical information I have found anywhere. With close to 1000 members any post
to the group will result in expert answers to any questions but you will have to be a member to post.
