I have an old 6 transistor radio (Spiket 2 Band, MW and LW) made in
Okenawa Japan. Complete with leather case, looks to be a late 1950s or
early 60s model.

The radio works well toward the lower end of the AM band and also upper
end, but reception drops off in the middle of the band around 800KHz,
but the reception is good if I touch the antenna loopstick.

I have tried to peak the antenna trimmer capacitor with no effect
around 800KHz, but the trimmer does peak the stations near the high
end.

I have also tried to adjust the main tuning capacitor along with the
oscillator coil to try and get a peak around 800Khz without success.

I have connected a generator to a couple turns of wire around the
antenna loopstick and monitored the signal on a scope. It tunes very
well and there is a sharp peak wherever I set the generator and tune
the cap. The local oscillator signal on the tuning capacitor also
looks good with fairly constant amplitude across the band.

It's a perplexing problem. Everything works well, but reception
is poor in the middle of the band.

Any ideas?

-Bill

wrote:
I have an old 6 transistor radio (Spiket 2 Band, MW and LW) made in
Okenawa Japan. Complete with leather case, looks to be a late 1950s or
early 60s model.

The radio works well toward the lower end of the AM band and also upper
end, but reception drops off in the middle of the band around 800KHz,
but the reception is good if I touch the antenna loopstick.

I have tried to peak the antenna trimmer capacitor with no effect
around 800KHz, but the trimmer does peak the stations near the high
end.

I have also tried to adjust the main tuning capacitor along with the
oscillator coil to try and get a peak around 800Khz without success.

I have connected a generator to a couple turns of wire around the
antenna loopstick and monitored the signal on a scope. It tunes very
well and there is a sharp peak wherever I set the generator and tune
the cap. The local oscillator signal on the tuning capacitor also
looks good with fairly constant amplitude across the band.

It's a perplexing problem. Everything works well, but reception
is poor in the middle of the band.

Any ideas?

-Bill

Hi Bill...

Wow, memories flooding back again

The trimmer should be peaked at the top of the dial.

Check to see if the wax has let go, and if the coil is loose(ish) on
the ferrite bar move it back and forth a bit to peak the low end.
(if it does, seal it in place again with a few drips of wax from a
burning candle)

Take care.

Ken

" bravely wrote to "All" (04 Oct 05 21:08:24)
--- on the heady topic of "Old 6 transistor Radio repair"

Bill,

First, I don't think tweaking everything within reach is a wise repair
technique (grains of salt). Try and set everything back the way it was
from the factory. Seems to me that the ferrite antenna is being loaded
down and is now over-critically damped, hence the double peak. Check
the gain of the mixer or rf amp transistor. Likely leaky electros due
to age? Might be a ps feedback or unfiltered agc making problems?

A*s*i*m*o*v


wr From:
wr Xref: core-easynews sci.electronics.repair:344196

wr I have an old 6 transistor radio (Spiket 2 Band, MW and LW) made in
wr Okenawa Japan. Complete with leather case, looks to be a late 1950s or
wr early 60s model.

wr The radio works well toward the lower end of the AM band and also
wr upper end, but reception drops off in the middle of the band around
wr 800KHz, but the reception is good if I touch the antenna loopstick.

wr I have tried to peak the antenna trimmer capacitor with no effect
wr around 800KHz, but the trimmer does peak the stations near the high
wr end.

wr I have also tried to adjust the main tuning capacitor along with the
wr oscillator coil to try and get a peak around 800Khz without success.

wr I have connected a generator to a couple turns of wire around the
wr antenna loopstick and monitored the signal on a scope. It tunes very
wr well and there is a sharp peak wherever I set the generator and tune
wr the cap. The local oscillator signal on the tuning capacitor also
wr looks good with fairly constant amplitude across the band.

wr It's a perplexing problem. Everything works well, but reception
wr is poor in the middle of the band.

wr Any ideas?

wr -Bill


.... If you don't know what leever "A" does then you better leever "B"

The trimmer should be peaked at the top of the dial.


Check to see if the wax has let go, and if the coil is loose(ish) on
the ferrite bar move it back and forth a bit to peak the low end.
(if it does, seal it in place again with a few drips of wax from a
burning candle)

Yes, I checked the antenna coil and it looks to be in good original
shape. There are 2 windings for the 540-1600Khz band and another
winding for the 160-340Khz overseas band.

I disconnected the overseas winding to check for loading on the other
band but no success.

The factory trimmer capacitor settings seem to be wrong since a couple
were set to maximum capacitance.

I think the problem is in the oscillator/mixer stage but I can't get
the main tuning dial off to get the circuit board out.
There is a emblem glued into the center of the tuning dial that covers
up a screw that holds on the tuning dial. I may have to drill it out to
get it off.

Problems and more problems.

-Bill

cxcvvcxvcv

wrote in message
oups.com...
I have an old 6 transistor radio (Spiket 2 Band, MW and LW) made in
Okenawa Japan. Complete with leather case, looks to be a late 1950s or
early 60s model.

The radio works well toward the lower end of the AM band and also upper
end, but reception drops off in the middle of the band around 800KHz,
but the reception is good if I touch the antenna loopstick.

I have tried to peak the antenna trimmer capacitor with no effect
around 800KHz, but the trimmer does peak the stations near the high
end.

I have also tried to adjust the main tuning capacitor along with the
oscillator coil to try and get a peak around 800Khz without success.

I have connected a generator to a couple turns of wire around the
antenna loopstick and monitored the signal on a scope. It tunes very
well and there is a sharp peak wherever I set the generator and tune
the cap. The local oscillator signal on the tuning capacitor also
looks good with fairly constant amplitude across the band.

It's a perplexing problem. Everything works well, but reception
is poor in the middle of the band.

Any ideas?

-Bill

bg wrote:
The IF amplifier also needs to be checked for the correct IF frequency,
because your tunnig L and C was designed to track at the IF frequency and
it will not track correctly at another frequency. Those IF trannys are very
tempting for inexperienced people to tweak.

With any of the LC tuned receivers, the inductance of the RF coil (which is
probably the loopstick), and the inductance of the oscillator coil is set
while the tunning capacitor is fully meshed. This is at the lowest RF
frequency. The RF and Osc trimmer caps are set at the high end of the dial
or when the tunning cap is fully unmeshed. Repeat the steps as neccessary to
get your best results at the extreme ends of the tunning range. If the
tracking goes bad in the midband, some tunning caps have slotted plates so
that the plates can be bent to improve the tracking, but this method is not
to common for low frequency cheap receivers.

Hi...

Darn! Does that mean that proper preventive maintenance doesn't mean
I need to tight all the screws down tight once in a while?

Not even those funny little ones hiding inside tin cans?

Ken

The IF amplifier also needs to be checked for the correct IF frequency,
because your tunnig L and C was designed to track at the IF frequency and
it will not track correctly at another frequency. Those IF trannys are very
tempting for inexperienced people to tweak.

With any of the LC tuned receivers, the inductance of the RF coil (which is
probably the loopstick), and the inductance of the oscillator coil is set
while the tunning capacitor is fully meshed. This is at the lowest RF
frequency. The RF and Osc trimmer caps are set at the high end of the dial
or when the tunning cap is fully unmeshed. Repeat the steps as neccessary to
get your best results at the extreme ends of the tunning range. If the
tracking goes bad in the midband, some tunning caps have slotted plates so
that the plates can be bent to improve the tracking, but this method is not
to common for low frequency cheap receivers.


wrote in message
.com...
I have an old 6 transistor radio (Spiket 2 Band, MW and LW) made in
Okenawa Japan. Complete with leather case, looks to be a late 1950s or
early 60s model.

The radio works well toward the lower end of the AM band and also upper
end, but reception drops off in the middle of the band around 800KHz,
but the reception is good if I touch the antenna loopstick.

I have tried to peak the antenna trimmer capacitor with no effect
around 800KHz, but the trimmer does peak the stations near the high
end.

I have also tried to adjust the main tuning capacitor along with the
oscillator coil to try and get a peak around 800Khz without success.

I have connected a generator to a couple turns of wire around the
antenna loopstick and monitored the signal on a scope. It tunes very
well and there is a sharp peak wherever I set the generator and tune
the cap. The local oscillator signal on the tuning capacitor also
looks good with fairly constant amplitude across the band.

It's a perplexing problem. Everything works well, but reception
is poor in the middle of the band.

Any ideas?

-Bill

bg wrote:
The IF amplifier also needs to be checked for the correct IF frequency,
because your tunnig L and C was designed to track at the IF frequency and
it will not track correctly at another frequency. Those IF trannys are very
tempting for inexperienced people to tweak.

With any of the LC tuned receivers, the inductance of the RF coil (which is
probably the loopstick), and the inductance of the oscillator coil is set
while the tunning capacitor is fully meshed. This is at the lowest RF
frequency. The RF and Osc trimmer caps are set at the high end of the dial
or when the tunning cap is fully unmeshed. Repeat the steps as neccessary to
get your best results at the extreme ends of the tunning range. If the
tracking goes bad in the midband, some tunning caps have slotted plates so
that the plates can be bent to improve the tracking, but this method is not
to common for low frequency cheap receivers.


Unfortunately, the problem cannot be fixed by any amount of tweeking.
It doesn't matter where the main tuning cap is set, and all the other
adjustments peaked at that point, oscillator, IF, trimmer caps, etc.
The result is always poor reception in the middle of the band. That's
why I can't figure it out. It doesn't make sense that with every
adjustment peaked at 800KHz, that point is sill weak. Yet if I sweep
the antenna coil and cap, it looks fairly flat on a scope. In other
words, there's nothing wrong, except it doesn't work.

-Bill

wrote:
bg wrote:

The IF amplifier also needs to be checked for the correct IF frequency,
because your tunnig L and C was designed to track at the IF frequency and
it will not track correctly at another frequency. Those IF trannys are very
tempting for inexperienced people to tweak.

With any of the LC tuned receivers, the inductance of the RF coil (which is
probably the loopstick), and the inductance of the oscillator coil is set
while the tunning capacitor is fully meshed. This is at the lowest RF
frequency. The RF and Osc trimmer caps are set at the high end of the dial
or when the tunning cap is fully unmeshed. Repeat the steps as neccessary to
get your best results at the extreme ends of the tunning range. If the
tracking goes bad in the midband, some tunning caps have slotted plates so
that the plates can be bent to improve the tracking, but this method is not
to common for low frequency cheap receivers.



Unfortunately, the problem cannot be fixed by any amount of tweeking.
It doesn't matter where the main tuning cap is set, and all the other
adjustments peaked at that point, oscillator, IF, trimmer caps, etc.
The result is always poor reception in the middle of the band. That's
why I can't figure it out. It doesn't make sense that with every
adjustment peaked at 800KHz, that point is sill weak. Yet if I sweep
the antenna coil and cap, it looks fairly flat on a scope. In other
words, there's nothing wrong, except it doesn't work.

Hi Bill...

Can't tell whether you're in a big city with lots of stations, or
a smaller one with just a few, so...

It's not possible that you're young enough not to have used these
back in the olden days, is it?

If so, and if you have only one or two stations in the middle of the
band, you should know that those antennas are highly directional.

Just in case...

Ken

"Priyan Perera" bravely wrote to "All" (06 Oct 05 15:23:13)
--- on the heady topic of " Old 6 transistor Radio repair"

PP From: "Priyan Perera"
PP Xref: core-easynews sci.electronics.repair:344274


PP cxcvvcxvcv


Even the babblefish is stumped!

A*s*i*m*o*v

.... "Hey, I'm just this guy, see?" --Zaphod Beeblebrox

On 10/6/05 1:43 PM, in article
,
" wrote:

bg wrote:
The IF amplifier also needs to be checked for the correct IF frequency,
because your tunnig L and C was designed to track at the IF frequency and
it will not track correctly at another frequency. Those IF trannys are very
tempting for inexperienced people to tweak.

With any of the LC tuned receivers, the inductance of the RF coil (which is
probably the loopstick), and the inductance of the oscillator coil is set
while the tunning capacitor is fully meshed. This is at the lowest RF
frequency. The RF and Osc trimmer caps are set at the high end of the dial
or when the tunning cap is fully unmeshed. Repeat the steps as neccessary to
get your best results at the extreme ends of the tunning range. If the
tracking goes bad in the midband, some tunning caps have slotted plates so
that the plates can be bent to improve the tracking, but this method is not
to common for low frequency cheap receivers.


Unfortunately, the problem cannot be fixed by any amount of tweeking.
It doesn't matter where the main tuning cap is set, and all the other
adjustments peaked at that point, oscillator, IF, trimmer caps, etc.
The result is always poor reception in the middle of the band. That's
why I can't figure it out. It doesn't make sense that with every
adjustment peaked at 800KHz, that point is sill weak. Yet if I sweep
the antenna coil and cap, it looks fairly flat on a scope. In other
words, there's nothing wrong, except it doesn't work.

-Bill


Have you watched the AGC voltage as you tune across the band? I suspect the
AGC is reducing the IF gain when you tune through the mid-band, due to a
stray oscillation. Could be caused by a bad capacitor on the AGC line. A
scope should show it.

Don

Have you watched the AGC voltage as you tune across the band? I suspect the
AGC is reducing the IF gain when you tune through the mid-band, due to a
stray oscillation. Could be caused by a bad capacitor on the AGC line. A
scope should show it.

The AGC seems to be working, since the reception is good on a weak
station near the lower end of the band. I can't imagine the AGC would
work at some points in the dial and not at others.

I did manage to get good reception in the middle band by adding another
antenna loopstick and capacitor. I used a few turns from the external
loopstick to couple the signal into the radio main loopstick with
another few turns.

Two loopsticks works better than one, but they won't both fit into the
same box.

-Bill

On 10/9/05 5:17 PM, in article
,
" wrote:

Have you watched the AGC voltage as you tune across the band? I suspect the
AGC is reducing the IF gain when you tune through the mid-band, due to a
stray oscillation. Could be caused by a bad capacitor on the AGC line. A
scope should show it.

The AGC seems to be working, since the reception is good on a weak
station near the lower end of the band. I can't imagine the AGC would
work at some points in the dial and not at others.

But I can imagine an IF oscillation at some part of the BC spectrum and not
at others - been there, fixed that.


I did manage to get good reception in the middle band by adding another
antenna loopstick and capacitor. I used a few turns from the external
loopstick to couple the signal into the radio main loopstick with
another few turns.

Two loopsticks works better than one, but they won't both fit into the
same box.

-Bill


Another thought is that someone screwed up the local oscillator, and it's
operating at 2x the I.F., low. This would prevent correct tuning of the
loop's trimmer.