Jon
You will always hear that microphonic sound when you tap a 1U5. It's the 1st audio amp and amplifies small signals.
The tube has a small filament supported by a spring at one end. When you tap the tube this filament vibrates and causes the noise. As long as you don't hear the ping when the radio is operating the tube is ok.
Norm
:When I turn on my T/O (R600), I hear a glassy tinkling sound from the speaker. If I tap the 1U5, I hear the tinkling noise. I replaced the 1U5 with another I had on hand and it still does it. Am I having bad luck with tubes, or could something else be going on here?
:
:Jon
Unfortunately, just pressing the band buttons will make the radio ping and send the radio into loud feedback squeals. The volume control has no effect on stopping the feedback, but turning the radio up too loud also starts the feedback. I have new bushings for the speaker to see if that helps, but I suspect it shouldn't be that sensitive. I've also found that just rubbing my finger across the top of the tube will make it start to squeal - is that normal? Filter caps have been replaced, and replacing the black beauties didn't help. I'm 1/2 way through the rest of the paper caps to see if they have any effect. Tuning on all bands in great - thank goodness I have a strong 1L6 or I'd probably give up on this freebie radio.
Jon
:Hi Jon
:
: You will always hear that microphonic sound when you tap a 1U5. It's the 1st audio amp and amplifies small signals.
:
: The tube has a small filament supported by a spring at one end. When you tap the tube this filament vibrates and causes the noise. As long as you don't hear the ping when the radio is operating the tube is ok.
:
:Norm
:
::When I turn on my T/O (R600), I hear a glassy tinkling sound from the speaker. If I tap the 1U5, I hear the tinkling noise. I replaced the 1U5 with another I had on hand and it still does it. Am I having bad luck with tubes, or could something else be going on here?
::
::Jon
Your pinging sound is from the 1U5 but doesn't mean it's bad. Selecting 1U5 tubes can help. Some radios have a large rubber band around the top of the 1U5. A shield may make a difference. Changing caps or any other components won't have an effect on 1U5 ping. Reducing overall again will help but that defeats your circuit.
Norm
:Thanks Norm,
:
: Unfortunately, just pressing the band buttons will make the radio ping and send the radio into loud feedback squeals. The volume control has no effect on stopping the feedback, but turning the radio up too loud also starts the feedback. I have new bushings for the speaker to see if that helps, but I suspect it shouldn't be that sensitive. I've also found that just rubbing my finger across the top of the tube will make it start to squeal - is that normal? Filter caps have been replaced, and replacing the black beauties didn't help. I'm 1/2 way through the rest of the paper caps to see if they have any effect. Tuning on all bands in great - thank goodness I have a strong 1L6 or I'd probably give up on this freebie radio.
:
:Jon
:
:
:
::Hi Jon
::
:: You will always hear that microphonic sound when you tap a 1U5. It's the 1st audio amp and amplifies small signals.
::
:: The tube has a small filament supported by a spring at one end. When you tap the tube this filament vibrates and causes the noise. As long as you don't hear the ping when the radio is operating the tube is ok.
::
::Norm
::
:::When I turn on my T/O (R600), I hear a glassy tinkling sound from the speaker. If I tap the 1U5, I hear the tinkling noise. I replaced the 1U5 with another I had on hand and it still does it. Am I having bad luck with tubes, or could something else be going on here?
:::
:::Jon
Thanks again,
Jon
:Hi Jon
:
: Your pinging sound is from the 1U5 but doesn't mean it's bad. Selecting 1U5 tubes can help. Some radios have a large rubber band around the top of the 1U5. A shield may make a difference. Changing caps or any other components won't have an effect on 1U5 ping. Reducing overall again will help but that defeats your circuit.
:
:Norm
: