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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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16th Dec 2019, 2:59 pm | #1 |
Tetrode
Join Date: Jan 2018
Location: Stockholm, Sweden
Posts: 78
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RCA AR88D band 3 partly dead
Hi Guys
Have tested all tubes with a TV-7/ tube tester and then replaced some tubes which tested below min level. -some improvement on all bands except band 3 which behaved very strange - först listening at normal levels then suddenly received signal went to the topp of the S-meter for a short while (a few seconds) then back to normal at the same time the sound also went up. Tested the tubes again and found that the "new" V3 (6J5) went of the scale on the TV-7/U, thus put the old 6J5 back and now Band 3 is dead from art 6.5 - 12MHz. However, the lower end of the band is OK. Have changed C33 and R6 but no improvement. R6 with nominal 33 K was degraded to 15.8 K. Does anyone have any suggestions where to start looking? Jan |
16th Dec 2019, 5:14 pm | #2 |
Hexode
Join Date: Jan 2013
Location: Kelvedon, Essex, UK.
Posts: 272
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Re: RCA AR88D band 3 partly dead
Have you cleaned the band change switch thoroughly?
John. |
16th Dec 2019, 6:32 pm | #3 |
Tetrode
Join Date: Jan 2018
Location: Stockholm, Sweden
Posts: 78
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Re: RCA AR88D band 3 partly dead
Hi John
Yes all switches are thoroughly cleaned. Jan |
17th Dec 2019, 9:48 am | #4 |
Hexode
Join Date: Jan 2013
Location: Kelvedon, Essex, UK.
Posts: 272
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Re: RCA AR88D band 3 partly dead
Have a look at my thread on my AR88D: https://www.vintage-radio.net/forum/...d.php?t=161439
It contains many fault finding tips from members. John. Last edited by AC/HL; 17th Dec 2019 at 2:55 pm. Reason: Link added |
19th Dec 2019, 4:25 pm | #5 |
Tetrode
Join Date: Jan 2018
Location: Stockholm, Sweden
Posts: 78
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Re: RCA AR88D band 3 partly dead
Hi again guys
Pleased to report PROBLEM SOLVED: The first problem was most probably that C21 was damaged by the faulty valve (V3) , then when replacing C21 and C23 the wire from C22 to C21 and L53 was connected to the wrong side of C21 i.e. to the junction of L53, C21 and C23 at tap 2 of L53. This affected only the higher end of band 3. Now the radio is at its normal self again and Band 3 is working again. Hope this can be of use to others Jan |
21st Dec 2019, 10:17 am | #6 |
Heptode
Join Date: Feb 2009
Location: Rotherham, South Yorkshire, UK.
Posts: 559
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Re: RCA AR88D band 3 partly dead
Hello Jan
I am pleased you have worked it out. Kevin |