Need Help On Blaupunkt Ballett
11/10/2011 11:21:57 AMBrianC(98086:0)
Picked up a Blaupunkt Ballett Radio Model #20013 the other day. It has 3 bands...the FM plays fine, the SW plays fine. The AM doesn't get any stations. If you tune to 550, you can hear it start to get some AM type static. If I put my Comcast TV remote control near the tuner and hit the remote buttons, I can hear the signal from the remote in the radio. Just wondering if I should look at the oscillator section, or tuning section. I have no schematic, and it is not easy to work on because of the PCB and cramped components in some areas. Tubes check out. I feel it could be out of alignment, but the trimmers looked untouched. And, if I touch one of the tuning can slugs with a screwdriver, I get a weird oscillation sound. Just need some guidance on where to go now. Thanks.
11/10/2011 9:45:03 PMBrianC(98095:98086)
:Picked up a Blaupunkt Ballett Radio Model #20013 the other day. It has 3 bands...the FM plays fine, the SW plays fine. The AM doesn't get any stations. If you tune to 550, you can hear it start to get some AM type static. If I put my Comcast TV remote control near the tuner and hit the remote buttons, I can hear the signal from the remote in the radio. Just wondering if I should look at the oscillator section, or tuning section. I have no schematic, and it is not easy to work on because of the PCB and cramped components in some areas. Tubes check out. I feel it could be out of alignment, but the trimmers looked untouched. And, if I touch one of the tuning can slugs with a screwdriver, I get a weird oscillation sound. Just need some guidance on where to go now. Thanks.
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11/10/2011 9:52:03 PMBrianC(98096:98095)
Here's another clue I found tonight....
It has a ferrite antenna..If I attach a length of wire to one of the 3 leads (from a smaller of the 2 coils on the rod), and hold it, I get AM stations, but they are talking over each other, and you can tune a little, but 1 station may take up almost 1/3 the dial. Any ideas where I can look? Or explain what may be happening here. I don't have a deep understanding of radio theory, but get the basic concepts. Just need a little guidance here.
11/10/2011 10:41:54 PMEdd(98100:98096)
Sir Brian Ceee. . . . .
Your findings with increased aerial input into the front end circuitry tends to sugggest it being swamped and just "TRF'ing" the strongest local stations right on thru, with the sets local oscillator-er-er circuitry being inactive. That would be result in having no superheterodyne action being present along with its acquired frequency selectivity and increased stage gain. Now I'm not even sure if I am anywhere near on that schematic . . . but on a probably similar Blaupunkt one, lets reference that and see if your set is using a ECH81 as its AM mixer oscillator.
As per the loop antenna circitry, additionaly, why not start by working those band switch contacts at least 50-100 times to be sure that is not just a case of oxide onset on those switch contacts with a LOOOOOONG dormant stored timespan.
If that ECH81 is the tube being used in your set, take a DVM or VTVM . . . . . from the aspect of its high Z and LOW loading . . . on measuring our involved 1st grid circuitry of the local oscillator.
In using DC metering with ground referencing, confirm if you have a NEGATIVE 4 on upwards to 7 volts DC on pin 9 of the sets ECH81.
Take a reading at both the low end and the high end of the AM BCB.
Thassit . . . pending your comeback . . . .
73's de Edd
Now, I am proofreading ever so carefully, to see if I have any words out.
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:Here's another clue I found tonight....
:It has a ferrite antenna..If I attach a length of wire to one of the 3 leads (from a smaller of the 2 coils on the rod), and hold it, I get AM stations, but they are talking over each other, and you can tune a little, but 1 station may take up almost 1/3 the dial. Any ideas where I can look? Or explain what may be happening here. I don't have a deep understanding of radio theory, but get the basic concepts. Just need a little guidance here.
:
11/11/2011 11:19:54 AMBrianC(98103:98100)
Edd, thanks for the help. I checked pin #9 on the ECH81 and got essentially zero volts across the dial, (just a few mv were there). Pin #8 plate was 53 volts.
The tube lineup for the radio is: ECH81--EF89--EABC80--EL84 and a diode pack rectifier.
Like I mentioned earlier, SW works fine, FM fine.
What's next?
11/11/2011 2:19:01 PMEdd(98104:98103)
Sir Brian Ceee. . . . .
Vell . . . .I'm bin tellink you vot . . . the next step would be to place the unit in the lowest frequency short waveless band and do the same test. That being because the relevant circuitry use is the same as used on the BCB , EXCEPTING the BCB oscillator coil and any BCB associated switching action/ circuitry. Also take a reading at both the low end and the high end of the SW band.
Thassit . . . pending your next comeback . . . .
73's de Edd
Definition . . . . Shin:
An anatomical feature for finding furniture in the dark.
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<:Edd, thanks for the help. I checked pin #9 on the ECH81 and got essentially zero volts across the dial, (just a few mv were there). Pin #8 plate was 53 volts.
:The tube lineup for the radio is: ECH81--EF89--EABC80--EL84 and a diode pack rectifier.
:Like I mentioned earlier, SW works fine, FM fine.
:What's next?
:
11/11/2011 3:32:38 PMBrianC(98107:98104)
OK...I tried the same test to pin 9 of the ECH81 with the SW on.....Got -4 to -5V, and plenty of stations. That should narrow it down now....
11/11/2011 9:07:05 PMBrianC(98112:98107)
OK...Found the problem....One of those fine hair wires off a front end AM/antenna tuning slug coil had broken it's connection...Re-connected, and good to go! Thanks Ed, you had me looking in the right area!!!
11/11/2011 2:29:30 PMWarren(98105:98103)
Pin 9 of the ECH81 should have negative volts in the AM position. The oscillator coil is switched by the AM-FM-SW selector buttons. The contacts need to be good and clean. It does not take much to stop the oscillator with resistance due to dirty contacts.