R106: HRO Senior Model
M
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I repaired
some minor faults many years ago and since then my brother-in-law,
Riki, kindly gave me the set. |
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The receiver uses UX-based
American valves having standard 6.3 volt heaters, although earlier
models used similar valves with 2.5 volt heaters. I'm not sure
why these latter types were selected because, with an external
power unit, resistive losses would be more critical.
The 6.3volt UX valves are basically
the same as the IO types: 6D6=6K7, 6C6=6J7, 6B7=6SQ7 and 42=6V6,
The 6D6 is variable mu allowing the AGC to change the stage gain. |
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The receiver has had only
one modification carried out which is the addition of an audio
output transformer. I'm puzzled why an internal transformer wasn't
included on the main chassis in the original design because,
apart from an external transformer being poor practice, it could
have been used for better headphone matching with extra audio
power. |
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This label is on the inside of the
hinged lid. |
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This label is on the underside of
the receiver. |
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The power supply that
arrived with this HRO, I believe may have been made by the late
G3AQY and the pictures show that it isn't what it first seemed.
The original HRO PSU was this shape and was referred to as a
"Dog House" power supply, but removing the cover reveals
more parts than the original. |
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There are three valves:
A 6V6G, EF80 and 0D3/VR150. |
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Inspection of the wiring
revealed some silicon diodes (covered by black sleeving) wired
to unused pins on the 0D3 stabiliser valve. Without tracing the
circuit I believe it's a regulated HT supply with a potentiometer
for setting the HRO HT voltage. A separate heater transformer
for the 6V6 & EF80 is located adjacent to the pair of blue
condensers. The loudspeaker is wired to the jack plug on the
front of the PSU and needs a cable wired to the rear of the R106
to where the new output transformer connects. |
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HRO
Coils at the Radio Museum
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Range |
Marked |
Notes |
50-100Kc/s |
- |
R106 |
50-100Kc/s |
- |
SSB HRO |
100-200Kc/s |
- |
R106 |
100-200Kc/s |
H657 |
SSB HRO |
180-430 Kc/s |
- |
R106, White on black label |
180-430 Kc/s |
H503 |
SSB HRO |
0.48-0.96Mc/s |
267 |
R106 |
0.48-0.96Mc/s |
H952 |
SSB HRO |
0.9-2.05Mc/s |
H520 |
R106 |
0.9-2.05Mc/s |
E331 |
SSB HRO |
1.7-4.0 Mc/s |
- |
R106, White on black label |
1.7-4.0 Mc/s |
B94 |
SSB HRO |
1.7-4.0 Mc/s |
H619 |
HRO Junior |
3.5-7.3Mc/s |
- |
R106, White on black label |
3.5-7.3Mc/s |
D296 |
HRO Junior |
3.5-7.3Mc/s |
H611 |
SSB HRO |
7-14.4Mc/s |
H658 |
R106 |
7-14.4Mc/s |
H753 |
HRO Junior |
7-14.4Mc/s |
D339 |
SSB HRO |
14-30Mc/s |
- |
R106, White on black label |
14-30Mc/s |
J386 |
SSB HRO |
10m |
H673, 14-30Mc/s |
Bandspread |
15m |
100-200Kc/s |
Bandspread SSB HRO |
20m |
- |
Bandspread SSB HRO |
20m |
- |
Bandspread SSB HRO Transceiver |
80m |
- |
Bandspread SSB HRO Transceiver |
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Below: the HF coil packs
with the R106 |
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More sets of coils |
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