HV transformers: Difference between revisions
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In many classic scopes, the high voltage transformer that supplies the cathode, blanking, and anode voltages has a tendency to break down. | In many classic scopes, the '''high voltage transformer''' that supplies the cathode, blanking, and anode voltages has a tendency to break down. | ||
This is mostly because of aging of the potting material used for the high-voltage windings. | This is mostly because of aging of the potting material used for the high-voltage windings. | ||
When this happens, the transformer will run very hot because dielectric loss is too high. | When this happens, the transformer will run very hot because dielectric loss is too high. | ||
| Line 10: | Line 10: | ||
This approach has been tested with success on a 556's HV transformer. | This approach has been tested with success on a 556's HV transformer. | ||
The same HV transformer, part number 120- | The same HV transformer, part number [[120-308]], is used in the [[543|543B]], [[544]], [[545|545B]], [[546]] and [[547]] . | ||
Chuck Harris, who frequents the Yahoo Tekscopes forum, has rebuilt several 120- | Chuck Harris, who frequents the groups.io (formerly Yahoo) Tekscopes forum, has rebuilt several 120-308 transformers with good results. | ||
==Documents== | |||
* [[Media:HV Transformer Tek 500 Series-Rev 02.pdf|"HV Transformers for Tektronix 500 Series Scopes Wound on ETD44 Core" by Marco Morelli]] | |||
==Pictures== | |||
<gallery> | <gallery> | ||
KeepcoolHV.JPG | Alternative to replacement: cooling with a heat sink | KeepcoolHV.JPG | Alternative to replacement: cooling with a heat sink | ||
120-466-0x.JPG | Two different HV transformers for [[561B]] & [[568]]. Brown potting ([[120-0466-00]]) is bad, clear potting ([[120-0466-01]]) is an improved variant to avoid the thermal runaway problems. | |||
</gallery> | </gallery> | ||
[[Category:Repair issues]] | [[Category:Repair issues]] | ||
[[Category: | [[Category:Inductors and transformers]] | ||
Latest revision as of 05:08, 7 April 2021
In many classic scopes, the high voltage transformer that supplies the cathode, blanking, and anode voltages has a tendency to break down. This is mostly because of aging of the potting material used for the high-voltage windings. When this happens, the transformer will run very hot because dielectric loss is too high. It is a thermal runaway.
Currently, the only options when this happens are to find a similar transformer from another scope, or to get a rewound transformer.
A second option is to improve the cooling of the high voltage transformer. This approach has been tested with success on a 556's HV transformer.
The same HV transformer, part number 120-308, is used in the 543B, 544, 545B, 546 and 547 . Chuck Harris, who frequents the groups.io (formerly Yahoo) Tekscopes forum, has rebuilt several 120-308 transformers with good results.
Documents
Pictures
-
Alternative to replacement: cooling with a heat sink
-
Two different HV transformers for 561B & 568. Brown potting (120-0466-00) is bad, clear potting (120-0466-01) is an improved variant to avoid the thermal runaway problems.
