Hi: I have an AK 55 that after some tinkering is playing again but the volumn is weak. I've checked the tubes, caps and resisters and all seem to be functioning ok. The plate voltages are stronger than the voltage table shows with the 45s around 300dc. The grids on both show -68. I've read on the forum that the input transformers are a common problem in this model. It appears someone replaced the transformer can at one point in its life. Could this be a source of the problem? I checked both and they both appear to have continunity. Any other thoughts? I am a weekend hobbyist at best so knowledge is limited. Thanks. Al

Hi Al

Voltages high but might be due to higher line voltage?

Bias of -68 is more negative than I would expect. Check the resistor divider network across the choke. Values should be 7,500 and 10,000 ohms. Too much bias will reduce volume.

Open audio interstage transformers are a common problem in old radios. Unless the wrong type was used as replacement shouldn't be a problem.

Be sure tuners track. You can move the antenna back one stage at a time for testing RF amplifiers.

Norm

:Hi: I have an AK 55 that after some tinkering is playing again but the volumn is weak. I've checked the tubes, caps and resisters and all seem to be functioning ok. The plate voltages are stronger than the voltage table shows with the 45s around 300dc. The grids on both show -68. I've read on the forum that the input transformers are a common problem in this model. It appears someone replaced the transformer can at one point in its life. Could this be a source of the problem? I checked both and they both appear to have continunity. Any other thoughts? I am a weekend hobbyist at best so knowledge is limited. Thanks. Al

:Thanks Norm. Your advice has saved several of my project radios. I'll follow up with your suggestions. Al

Hi Al
:
: Voltages high but might be due to higher line voltage?
:
: Bias of -68 is more negative than I would expect. Check the resistor divider network across the choke. Values should be 7,500 and 10,000 ohms. Too much bias will reduce volume.
:
: Open audio interstage transformers are a common problem in old radios. Unless the wrong type was used as replacement shouldn't be a problem.
:
: Be sure tuners track. You can move the antenna back one stage at a time for testing RF amplifiers.
:
: Norm
:
::Hi: I have an AK 55 that after some tinkering is playing again but the volumn is weak. I've checked the tubes, caps and resisters and all seem to be functioning ok. The plate voltages are stronger than the voltage table shows with the 45s around 300dc. The grids on both show -68. I've read on the forum that the input transformers are a common problem in this model. It appears someone replaced the transformer can at one point in its life. Could this be a source of the problem? I checked both and they both appear to have continunity. Any other thoughts? I am a weekend hobbyist at best so knowledge is limited. Thanks. Al