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Selector
Switch At:
Tube
Meter
Readings:
1
RCA -1620,
in Pre -Amplifier #1
70* 10
2
RCA -1620,
in Pre -Amplifier #2
70 ± 10
3
RCA -1620,
in Pre -Amplifier #3
70* 10
4
RCA -1620,
in Pre -Amplifier in
70* 10
5
RCA -1620, 1st Stage of Prog. Amp.
70* 10
6
RCA -1620, 1st Stage of Mon. Amp.
70 ± 10
7
RCA -1620, 2nd Stage of Prog. Amp.
70 ± 10
8
RCA -1620, 3rd Stage of Prog. Amp.
70+10
9
RCA -1621, Output Stage of Prog. Amp
70 ± 10
10
RCA -1621, Output Stage of Prog. Amp
70 ± 10
In order to obtain bias voltage readings, the volume indicator switch must be first turned to the
"Off" position.
The t ube socket and Radiotron cap contacts should be cleaned with carbon tetrachloride or crocus
cloth every three months to insure noiseless operation.
The mixer and master control contacts should be cleaned by applying "Davenoil" to the contacts,
rotating the knob, and if any dark streaks appear, wiping off the contacts.
Repeat this procedure until
absolutely clean, then lubricate with a thin film of "Davenoil" included as part of this equipment.
IMPORTANT:
The Davenoil
is provided for cleaning and lubricating the contacts of the mixers and volume
controls; and no other cleaning agent such as carbon tetrachloride, should be used.
is.
CARE OF CONTROL SWITCHES
Cleani ng and lubrication of the push button switches should not be necessary during their normal
life.
The contacts are heavily silver plated, and because of the wiping contact, should give no trouble
for noise or poor contact.
However,
if for some reason it should become necessary to clean and lubricate the push button
switches, proceed as follows:
To clean use a small amount of carbon tetrachloride or Energine and apply very carefully with
a small brush.
Relubricate using the small tin of special grease provided.
Apply very
sparingly with a small brush to eliminate the possibility of picking up floating dust and
di rt in the air.
Do not lift contacts to clean or lubricate.
Only in rare instances, or in case of damage due to tampering, should it become necessary to ad-
just the contacts of the push button switches.
A small tool such as is used to adjust relay or key
switch contacts will be required.
The contact fingers should be formed near the insulation to increase
the tension.
Never bend the contact finger in the middle or near the contact "dimple".
These switches
are quite easily removed from the front panel by removing the screws at the extremes of the buttons.
As shipped from the factory the various key switch contacts have been properly adjusted to give
the proper sequence of circuit connections when they are operated, so that a microphone and speaker will
not be on at one time in the same studio and in this way cause acoustic feedback.
In case a replace-
ment key switch is installed or if feedback trouble is encountered, the contacts should be adjusted
using a standard key switch or relay contact bending tool.
When adjusting the switches the following
desired sequence of operations should. be kept in mind.
THE RELAY CONTACTS MUST OPERATE FIRST AND THE
AUDIO CIRCUITS TRANSFER LAST.
This is accomplished by relieving the tension of the center spring of
the form D contacts controlling the relays, and increasing the tension of the center spring of the
form D contacts carrying audio.
Care should be taken that the spring shape is not altered or the
contact pressure reduced so much as to cause poor contact or short circuits.
To remove the key switch
- 30 -
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