Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
Repairing an old Grundig tube radio
I have a Grundig tube radio - 4070U - which I love dearly. I bought it
almost five years ago and had it restored by someone who knew what he was doing. I no longer live in the same area and can't benefit from his services again. It has two problems. The right channel cuts out intermittently. The sound can be restored in two ways: if I turn the volume way up, or (sometimes) if I give it a rap on the case. In both situations, the sound is restored with a small pop. In addition, the sound also returns if I do nothing, i.e., if I wait a few minutes. But then of course it disappears again. The other problem is that the sound in the left channel is extremely weak. It is possible to hear it if the right channel has cut out, so something is arriving at the speaker, but not much. This one is not an intermittent problem. The restoration in 2001 included replacement of capacitors. Not sure if it included replacement of tubes. Any suggestions received with gratitude. |
#2
Posted to sci.electronics.repair
|
|||
|
|||
Repairing an old Grundig tube radio
"grupt" wrote in message ps.com... I have a Grundig tube radio - 4070U - which I love dearly. I bought it almost five years ago and had it restored by someone who knew what he was doing. I no longer live in the same area and can't benefit from his services again. It has two problems. The right channel cuts out intermittently. The sound can be restored in two ways: if I turn the volume way up, or (sometimes) if I give it a rap on the case. In both situations, the sound is restored with a small pop. In addition, the sound also returns if I do nothing, i.e., if I wait a few minutes. But then of course it disappears again. The other problem is that the sound in the left channel is extremely weak. It is possible to hear it if the right channel has cut out, so something is arriving at the speaker, but not much. This one is not an intermittent problem. The restoration in 2001 included replacement of capacitors. Not sure if it included replacement of tubes. Any suggestions received with gratitude. The intermittent right channel will likely be something very simple, such as a bad joint or dirty tube base, but the low level left channel is likely to be something more challenging, and if you don't have any experience working on this sort of kit, is probably best left to someone who does. Just one quick thought though. Some of these old radios had a ' GRAM ' input on the back for a record deck, and a selector switch, sometimes part of the wavechange switch. If this were the case on yours, could be bad switch contacts, particularly if you don't change band very often. Could even still be this if it doesn't have a gram input. You might try giving the bandchange switch a vigorous scrub back and forth if its a rotary type, or a good " working " if it's the old Grundig piano keys. As far as going inside yourself, the high voltages involved can be dangerous, and I would hate for you to get a serious electric shock. If you have any old mom and pop TV shops in your area, there's bound to be someone there who is still tube-savvy, and could sort these problems for you. Failing this, bit more of a long shot, but there are still lots of tube amps in use by musicians. If you have a local musical instrument store that takes in repairs, they will likely know someone experienced in tube equipment repairs, that may be able to help. Arfa |
#4
Posted to sci.electronics.repair
|
|||
|
|||
Repairing an old Grundig tube radio
Matti,
Why do you oppose cleaning the tube pins with sandpaper / emory cloth ? Just curious as I've done that before as well as using a very small round file to clean the pins of the tube socket. |
#5
Posted to sci.electronics.repair
|
|||
|
|||
Repairing an old Grundig tube radio
grupt wrote:
I have a Grundig tube radio - 4070U - which I love dearly. I bought it almost five years ago and had it restored by someone who knew what he was doing. I no longer live in the same area and can't benefit from his services again. It has two problems. The right channel cuts out intermittently. The sound can be restored in two ways: if I turn the volume way up, or (sometimes) if I give it a rap on the case. In both situations, the sound is restored with a small pop. In addition, the sound also returns if I do nothing, i.e., if I wait a few minutes. But then of course it disappears again. The other problem is that the sound in the left channel is extremely weak. It is possible to hear it if the right channel has cut out, so something is arriving at the speaker, but not much. This one is not an intermittent problem. The restoration in 2001 included replacement of capacitors. Not sure if it included replacement of tubes. Any suggestions received with gratitude. Start by swapping Speakers R/L - L/R ! even if it means you must unsolder to swap speaker leads. Yukio YANO |
#6
Posted to sci.electronics.repair
|
|||
|
|||
Repairing an old Grundig tube radio
In article . com, says...
Matti, Why do you oppose cleaning the tube pins with sandpaper / emory cloth ? Just curious as I've done that before as well as using a very small round file to clean the pins of the tube socket. Because these tools are scratching surfaces. Especially if you have silver plated pins or socket these are gone if you use file or sanding for removing oxidation. All the tiny scratches can oxidate and the cleaning is harder and harder in the future. The pencileraser (if you are able to find one) is very good when cleaning all kind of connectors. There is one exception. If the equipment has sensitive electronics this pen can produce some high voltage which can destroy something. Never happened to me. Other nice tool cor cleaning connectors is glass fiber pen. Its is very sensitive method but you must be aware of tiny glass fiber "threads" which easily cut off. They can penetrate your skin. If you want use emery paper please use 1200 which is very very fine. Or you can use "used" 600 paper. Cleaning the sockets is harder. I use alcohol and tiny carved woodstick. -- Matti Kaki at iki dot fi http://www.sci.fi/~oh2bio =========== Location: 60.414 N 25.097 E =========== Navigare Necesse Est - Vivere Non Est Necesse |
#7
Posted to sci.electronics.repair
|
|||
|
|||
Repairing an old Grundig tube radio
I do remember the old static problem, supposedly caused by rubbing edge
connectors with the eraser. Never did see any damage (no recalls). I pulled a few fiberglass pen fibers out my finger too and gave up on using them. I've worked in the A/V and Instrument repair business for over 30 years, sounds like we have similar experience. Take Care, Kevin |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Wayne Dalton Torquemaster and iDrive self-Install (Long) | Home Repair | |||
Replacement picture tube out of warranty? | Electronics Repair | |||
Tech Review: Victor's (8liners/Genao) Replacement Arcade RGB Monitor Chassis (LONG) | Electronics Repair | |||
metal tubes | Metalworking | |||
Improve Sensitivity on Radio | Electronics |