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Posted to rec.audio.tech
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On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote:
Hi, I'm almost finished restoring a KLH Model 21. I replaced three transistors on the RF board and it now works! The only problem left is a hum from the audio board. I disconnected it from the input to the board so I'm sure it's not coming from anywhere else. I replaced the filter capacitor and all electrolytics on the audio board and it's a little quieter, but still there. The level of the hum doesn't change with the volume control. Any hints would be appreciated! Thanks, Mitch Hi Mitch. The power supply filters, either of the black color are/were a common failure item. They should be replaced. However, note that the positive terminal was marked with the stripe as we would now associate with the negative terminal. It is also important that you do not increase the value of these capacitors as the power supply can't handle the extra in-rush and operational paramete5rs. Mark - Former National Service Manager, KLH Cambridge.. |
#2
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Posted to rec.audio.tech
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#4
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Posted to rec.audio.tech
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On 18/03/2018 11:08 AM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote: On 17/03/2018 1:22 AM, wrote: On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote: Hi, I'm almost finished restoring a KLH Model 21. I replaced three transistors on the RF board and it now works! The only problem left is a hum from the audio board. I disconnected it from the input to the board so I'm sure it's not coming from anywhere else. I replaced the filter capacitor and all electrolytics on the audio board and it's a little quieter, but still there. The level of the hum doesn't change with the volume control. Any hints would be appreciated! Thanks, Mitch Hi Mitch. The power supply filters, either of the black color are/were a common failure item. They should be replaced. However, note that the positive terminal was marked with the stripe as we would now associate with the negative terminal. It is also important that you do not increase the value of these capacitors as the power supply can't handle the extra in-rush and operational paramete5rs. Mark - Former National Service Manager, KLH Cambridge. Wonder whether he even still has it 17 years later? :-) Probably not - at least not with the issue still (however somebody might...) It's good to have a knowledgeable person posting here so let's not be too harsh... True, might help someone else, and I wouldn't want to discourage that. I'm just amazed at how many people answer 20 year old posts because they don't even realise it. :-) Trevor. |
#5
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Posted to rec.audio.tech
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Once upon a time on usenet Trevor wrote:
On 18/03/2018 11:08 AM, ~misfit~ wrote: Once upon a time on usenet Trevor wrote: On 17/03/2018 1:22 AM, wrote: On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote: Hi, I'm almost finished restoring a KLH Model 21. I replaced three transistors on the RF board and it now works! The only problem left is a hum from the audio board. I disconnected it from the input to the board so I'm sure it's not coming from anywhere else. I replaced the filter capacitor and all electrolytics on the audio board and it's a little quieter, but still there. The level of the hum doesn't change with the volume control. Any hints would be appreciated! Thanks, Mitch Hi Mitch. The power supply filters, either of the black color are/were a common failure item. They should be replaced. However, note that the positive terminal was marked with the stripe as we would now associate with the negative terminal. It is also important that you do not increase the value of these capacitors as the power supply can't handle the extra in-rush and operational paramete5rs. Mark - Former National Service Manager, KLH Cambridge. Wonder whether he even still has it 17 years later? :-) Probably not - at least not with the issue still (however somebody might...) It's good to have a knowledgeable person posting here so let's not be too harsh... True, might help someone else, and I wouldn't want to discourage that. I'm just amazed at how many people answer 20 year old posts because they don't even realise it. :-) As you likely know it's usually because these days most people don't actually use usenet - they use parasitic web forums that don't delete old posts in an effort to appear to have lots of content. Cheers, -- Shaun. "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders) |
#6
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Posted to rec.audio.tech
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On 19/03/2018 1:05 PM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote: On 18/03/2018 11:08 AM, ~misfit~ wrote: Once upon a time on usenet Trevor wrote: On 17/03/2018 1:22 AM, wrote: On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote: Hi, I'm almost finished restoring a KLH Model 21. I replaced three transistors on the RF board and it now works! The only problem left is a hum from the audio board. I disconnected it from the input to the board so I'm sure it's not coming from anywhere else. I replaced the filter capacitor and all electrolytics on the audio board and it's a little quieter, but still there. The level of the hum doesn't change with the volume control. Any hints would be appreciated! Thanks, Mitch Hi Mitch. The power supply filters, either of the black color are/were a common failure item. They should be replaced. However, note that the positive terminal was marked with the stripe as we would now associate with the negative terminal. It is also important that you do not increase the value of these capacitors as the power supply can't handle the extra in-rush and operational paramete5rs. Mark - Former National Service Manager, KLH Cambridge. Wonder whether he even still has it 17 years later? :-) Probably not - at least not with the issue still (however somebody might...) It's good to have a knowledgeable person posting here so let's not be too harsh... True, might help someone else, and I wouldn't want to discourage that. I'm just amazed at how many people answer 20 year old posts because they don't even realise it. :-) As you likely know it's usually because these days most people don't actually use usenet - they use parasitic web forums that don't delete old posts in an effort to appear to have lots of content. Yes I know, and many are from Google Groups, but I would have thought the date was still shown somewhere? But then I've never used it myself. Trevor. |
#7
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Posted to rec.audio.tech
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Once upon a time on usenet Trevor wrote:
On 19/03/2018 1:05 PM, ~misfit~ wrote: Once upon a time on usenet Trevor wrote: On 18/03/2018 11:08 AM, ~misfit~ wrote: Once upon a time on usenet Trevor wrote: On 17/03/2018 1:22 AM, wrote: On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote: Hi, I'm almost finished restoring a KLH Model 21. I replaced three transistors on the RF board and it now works! The only problem left is a hum from the audio board. I disconnected it from the input to the board so I'm sure it's not coming from anywhere else. I replaced the filter capacitor and all electrolytics on the audio board and it's a little quieter, but still there. The level of the hum doesn't change with the volume control. Any hints would be appreciated! Thanks, Mitch Hi Mitch. The power supply filters, either of the black color are/were a common failure item. They should be replaced. However, note that the positive terminal was marked with the stripe as we would now associate with the negative terminal. It is also important that you do not increase the value of these capacitors as the power supply can't handle the extra in-rush and operational paramete5rs. Mark - Former National Service Manager, KLH Cambridge. Wonder whether he even still has it 17 years later? :-) Probably not - at least not with the issue still (however somebody might...) It's good to have a knowledgeable person posting here so let's not be too harsh... True, might help someone else, and I wouldn't want to discourage that. I'm just amazed at how many people answer 20 year old posts because they don't even realise it. :-) As you likely know it's usually because these days most people don't actually use usenet - they use parasitic web forums that don't delete old posts in an effort to appear to have lots of content. Yes I know, and many are from Google Groups, but I would have thought the date was still shown somewhere? But then I've never used it myself. Nor have I - at least not for posting. Once or twice I've tried to search for an old post. The *******s took over Deja news archives and butchered them! -- Shaun. "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders) |
#8
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Posted to rec.audio.tech
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On 18/03/2018 1:08 PM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote: On 17/03/2018 1:22 AM, wrote: On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote: Hi, I'm almost finished restoring a KLH Model 21. I replaced three transistors on the RF board and it now works! The only problem left is a hum from the audio board. I disconnected it from the input to the board so I'm sure it's not coming from anywhere else. I replaced the filter capacitor and all electrolytics on the audio board and it's a little quieter, but still there. The level of the hum doesn't change with the volume control. Any hints would be appreciated! Thanks, Mitch Hi Mitch. The power supply filters, either of the black color are/were a common failure item. They should be replaced. However, note that the positive terminal was marked with the stripe as we would now associate with the negative terminal. It is also important that you do not increase the value of these capacitors as the power supply can't handle the extra in-rush and operational paramete5rs. Mark - Former National Service Manager, KLH Cambridge. Wonder whether he even still has it 17 years later? :-) Trevor. Probably not - at least not with the issue still (however somebody might...) It's good to have a knowledgeable person posting here so let's not be too harsh... Jeeze Shaun - you stalking me or something - you're everywhere ! geoff |
#9
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Posted to rec.audio.tech
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Once upon a time on usenet geoff wrote:
On 18/03/2018 1:08 PM, ~misfit~ wrote: Once upon a time on usenet Trevor wrote: On 17/03/2018 1:22 AM, wrote: On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote: Hi, I'm almost finished restoring a KLH Model 21. I replaced three transistors on the RF board and it now works! The only problem left is a hum from the audio board. I disconnected it from the input to the board so I'm sure it's not coming from anywhere else. I replaced the filter capacitor and all electrolytics on the audio board and it's a little quieter, but still there. The level of the hum doesn't change with the volume control. Any hints would be appreciated! Thanks, Mitch Hi Mitch. The power supply filters, either of the black color are/were a common failure item. They should be replaced. However, note that the positive terminal was marked with the stripe as we would now associate with the negative terminal. It is also important that you do not increase the value of these capacitors as the power supply can't handle the extra in-rush and operational paramete5rs. Mark - Former National Service Manager, KLH Cambridge. Wonder whether he even still has it 17 years later? :-) Trevor. Probably not - at least not with the issue still (however somebody might...) It's good to have a knowledgeable person posting here so let's not be too harsh... Jeeze Shaun - you stalking me or something Says the man replying to me... - you're everywhere ! I prefer omnipresent. ;-) -- Shaun. "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders) |
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