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
|
|||
|
|||
Why were old transformers coated with tar?
I remember a lot of old transformers, particularly the power
transformers on the old TV sets, were coated with tar. It was not a real problem, but was kind of ugly, particularly when the wires had tar all over them. What was the purpose for the tar? My guess was to eliminate chattering of the steel laminations. Yet, it seems the practice of using tar vanished for the most part in the 70s and later. Yet I have not seen any untarred modern transformers chatter...... I will add to this, that the most chattering I have heard from transformers are the small ones which do NOT have bolts going thru the core, such as filament transformers and doorbell transformers. Several times over the years I have had people ask me why there is a noisy sound in their basement and it never fails, it's the doorbell transformer. This could often be fixed by squeezing the outer metal piece against the laminations, and applying something like laquer or silicone caulk. However, for the small price they cost, I usually just replaced them with a new one. |
#2
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
|
#3
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
On Tuesday, 15 January 2019 03:24:57 UTC, wrote:
I remember a lot of old transformers, particularly the power transformers on the old TV sets, were coated with tar. It was not a real problem, but was kind of ugly, particularly when the wires had tar all over them. What was the purpose for the tar? My guess was to eliminate chattering of the steel laminations. Yet, it seems the practice of using tar vanished for the most part in the 70s and later. Yet I have not seen any untarred modern transformers chatter...... I will add to this, that the most chattering I have heard from transformers are the small ones which do NOT have bolts going thru the core, such as filament transformers and doorbell transformers. Several times over the years I have had people ask me why there is a noisy sound in their basement and it never fails, it's the doorbell transformer. This could often be fixed by squeezing the outer metal piece against the laminations, and applying something like laquer or silicone caulk. However, for the small price they cost, I usually just replaced them with a new one. Modern transformers use clear stuff for the same purpose. It stops noises & holds the windings etc in place. NT |
#5
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
People put tar on airgun springs to remove noise and smooth out firing.
That's not the ideal way, but that requires precisely fitted spring guides adjusted for the individual airgun, and that doesn't happen in manufacturing. |
#6
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
Look165 wrote:
Once, winded and assembled, the pieces were put in a resin we call "jaja" in France. And then put in an under-pressurized "bubble room" for completing the process. When there was no more bubbles, the process was over. ** The process is commonly known as " vacuum impregnation " - completed transformers are placed in tank of resin or varnish and the air pressure reduced until all air pockets are filled. Not always done with bobbin wound transformers but standard practice with layer wound and old style cloth insulated toroidal mains transformers plus any tranny that handles substantial voltages. ..... Phil Resin (or tar) is there for noise suppression, mechanical fixing of the windings and insulation improvement. a écrit le 15/01/2019 Ã* 12:36Â*: On Tuesday, 15 January 2019 03:24:57 UTC, wrote: I remember a lot of old transformers, particularly the power transformers on the old TV sets, were coated with tar. It was not a real problem, but was kind of ugly, particularly when the wires had tar all over them. What was the purpose for the tar? My guess was to eliminate chattering of the steel laminations. Yet, it seems the practice of using tar vanished for the most part in the 70s and later. Yet I have not seen any untarred modern transformers chatter...... I will add to this, that the most chattering I have heard from transformers are the small ones which do NOT have bolts going thru the core, such as filament transformers and doorbell transformers. Several times over the years I have had people ask me why there is a noisy sound in their basement and it never fails, it's the doorbell transformer. This could often be fixed by squeezing the outer metal piece against the laminations, and applying something like laquer or silicone caulk. However, for the small price they cost, I usually just replaced them with a new one. Modern transformers use clear stuff for the same purpose. It stops noises & holds the windings etc in place. NT |
#7
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
Excuse my English, I am French.
Phil Allison a écrit le 15/01/2019 Ã* 18:13Â*: Look165 wrote: Once, winded and assembled, the pieces were put in a resin we call "jaja" in France. And then put in an under-pressurized "bubble room" for completing the process. When there was no more bubbles, the process was over. ** The process is commonly known as " vacuum impregnation " - completed transformers are placed in tank of resin or varnish and the air pressure reduced until all air pockets are filled. Not always done with bobbin wound transformers but standard practice with layer wound and old style cloth insulated toroidal mains transformers plus any tranny that handles substantial voltages. .... Phil Resin (or tar) is there for noise suppression, mechanical fixing of the windings and insulation improvement. a écrit le 15/01/2019 Ã* 12:36Â*: On Tuesday, 15 January 2019 03:24:57 UTC, wrote: I remember a lot of old transformers, particularly the power transformers on the old TV sets, were coated with tar. It was not a real problem, but was kind of ugly, particularly when the wires had tar all over them. What was the purpose for the tar? My guess was to eliminate chattering of the steel laminations. Yet, it seems the practice of using tar vanished for the most part in the 70s and later. Yet I have not seen any untarred modern transformers chatter...... I will add to this, that the most chattering I have heard from transformers are the small ones which do NOT have bolts going thru the core, such as filament transformers and doorbell transformers. Several times over the years I have had people ask me why there is a noisy sound in their basement and it never fails, it's the doorbell transformer. This could often be fixed by squeezing the outer metal piece against the laminations, and applying something like laquer or silicone caulk. However, for the small price they cost, I usually just replaced them with a new one. Modern transformers use clear stuff for the same purpose. It stops noises & holds the windings etc in place. NT |
#8
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
On 1/15/19 11:13 AM, Phil Allison wrote:
** The process is commonly known as " vacuum impregnation " - completed transformers are placed in tank of resin or varnish and the air pressure reduced until all air pockets are filled. Actually, the vacuum allows the bubbles to expand enough to float to the surface and pop. I did this with hand wound transformers at TRW using Poly Urethane, and in my shop mostly with casting resins. The vacuum chambers at TRW were nice, but I found that using a modified pressure cooker works fine for the size jobs I have. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
#9
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
For me, it was telecom transformers for SNCF.
Fox's Mercantile a écrit le 15/01/2019 Ã* 19:51Â*: On 1/15/19 11:13 AM, Phil Allison wrote: ** The process is commonly known as " vacuum impregnation " -Â* completed transformers are placed inÂ* tank of resin or varnish and the air pressure reduced until all air pockets are filled. Actually, the vacuum allows the bubbles to expand enough to float to the surface and pop. I did this with hand wound transformers at TRW using Poly Urethane, and in my shop mostly with casting resins. The vacuum chambers at TRW were nice, but I found that using a modified pressure cooker works fine for the size jobs I have. |
#10
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
On Monday, January 14, 2019 at 7:24:57 PM UTC-8, wrote:
I remember a lot of old transformers, particularly the power transformers on the old TV sets, were coated with tar. There are mechanical forces between wires carrying current, and in addition to making 'hum' that puts some metal fatigue into the mix. For reliability, especially for switchmode, vacuum impregnation or some other secure-the-wires provision is common in power inductors. At low frequencies, you can get away with oil and paper. Or thick oil (asphalt, tar...). |
#11
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
That's true, I forgot the magnetostriction.
But it's only true for LF ; with HF (some 10 kHz), the inertial forces are too strong and too much low in movement. whit3rd a écrit le 16/01/2019 Ã* 05:42Â*: On Monday, January 14, 2019 at 7:24:57 PM UTC-8, wrote: I remember a lot of old transformers, particularly the power transformers on the old TV sets, were coated with tar. There are mechanical forces between wires carrying current, and in addition to making 'hum' that puts some metal fatigue into the mix. For reliability, especially for switchmode, vacuum impregnation or some other secure-the-wires provision is common in power inductors. At low frequencies, you can get away with oil and paper. Or thick oil (asphalt, tar...). |
#12
Posted to sci.electronics.repair
|
|||
|
|||
Why were old transformers coated with tar?
|
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
how to remove old roofing tar from brick wall | Home Repair | |||
Wood fence post coated with tar? | Home Repair | |||
Old Black Tar Floor Adhesive--Safety Question | Home Repair | |||
vinyl coated vs. pvc coated aluminum | Home Repair | |||
Phosphor coated drywall screws - why? | UK diy |