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545B Repair

Juri Ghisio Member Profile All Messages By This Member #77853 Hello, Recently I received a new power transformer for my 545B, the old one was died under my eyes during troubleshooting. I have substituted the transformer and power up unit slowly with variac, the primary current seems to be ok is about 2.4A @ 230Vac about 550VA but some regulated ( 350V and 500V) supply was bad. I have recheck electrolitic capacitors seems to be ok. I have notice that there is some resistors after rectifier (R760, R730, R700, R670, R640 and R802 on H.V. supply), Have anyone the voltage drop accross this resistor of a working unit in order to know power absorption? I also have a working 535A, the power supply is very similar, I can measure the voltage drop of resistore mentioned above in this unit to get an idea or the current consumption is more different?? Juri
PA4TIM All Messages By This Member #77854 The 535A has a different HV supply a the 545B. I have both, ( non working). My HV transformer from the 545B is dead too but i have not repaired it because I now have a 547. If you look in the archives there is a discussion I tarted about this and Albert and I did some comparing meaurements. So probably you find there what you are looking for. On my site I have published it too, but the server is down ( and my friend who's server this is, is on holyday, so I am afraid this will take some time) The 535A has a wax impregnated transformer, the 547 a epoxy dipped one. Many repacement transformers that are kept in colder and moisture places are bad. My 545B had no problem. When i got it I irst used it while it was 30 degrees Celcius. No poblem. Used it some time without poblems but because of the space it moved to the garage and stayed there during winter. When i took it out I could use it about an hour max beore the transformer saturated. Fred toggle quoted message Show quoted text --- In TekScopes@..., "yurighisio" <yurighisio@...> wrote: Hello, Recently I received a new power transformer for my 545B, the old one was died under my eyes during troubleshooting. I have substituted the transformer and power up unit slowly with variac, the primary current seems to be ok is about 2.4A @ 230Vac about 550VA but some regulated ( 350V and 500V) supply was bad. I have recheck electrolitic capacitors seems to be ok. I have notice that there is some resistors after rectifier (R760, R730, R700, R670, R640 and R802 on H.V. supply), Have anyone the voltage drop accross this resistor of a working unit in order to know power absorption? I also have a working 535A, the power supply is very similar, I can measure the voltage drop of resistore mentioned above in this unit to get an idea or the current consumption is more different?? Juri
Juri Ghisio Member Profile All Messages By This Member #77857 Hello, I have "only" problem with low voltage power supply, the crt circuit seems to be ok. Juri toggle quoted message Show quoted text --- In TekScopes@..., "fred" <fredschneider@...> wrote: The 535A has a different HV supply a the 545B. I have both, ( non working). My HV transformer from the 545B is dead too but i have not repaired it because I now have a 547. If you look in the archives there is a discussion I tarted about this and Albert and I did some comparing meaurements. So probably you find there what you are looking for. On my site I have published it too, but the server is down ( and my friend who's server this is, is on holyday, so I am afraid this will take some time) The 535A has a wax impregnated transformer, the 547 a epoxy dipped one. Many repacement transformers that are kept in colder and moisture places are bad. My 545B had no problem. When i got it I irst used it while it was 30 degrees Celcius. No poblem. Used it some time without poblems but because of the space it moved to the garage and stayed there during winter. When i took it out I could use it about an hour max beore the transformer saturated. Fred --- In TekScopes@..., "yurighisio" <yurighisio@> wrote: Hello, Recently I received a new power transformer for my 545B, the old one was died under my eyes during troubleshooting. I have substituted the transformer and power up unit slowly with variac, the primary current seems to be ok is about 2.4A @ 230Vac about 550VA but some regulated ( 350V and 500V) supply was bad. I have recheck electrolitic capacitors seems to be ok. I have notice that there is some resistors after rectifier (R760, R730, R700, R670, R640 and R802 on H.V. supply), Have anyone the voltage drop accross this resistor of a working unit in order to know power absorption? I also have a working 535A, the power supply is very similar, I can measure the voltage drop of resistore mentioned above in this unit to get an idea or the current consumption is more different?? Juri
Mike All Messages By This Member #77937 Juri- You did not mention if regulated +500 and +350 were high or low, or whether their raw supplies are OK (about 600 and 490 respectively)? I'm assuming your -150 (reference supply) is in spec. Since the +500 regulator V754's cathode return depends on +350, I'd start by looking at the +350 regulator. For example, there's a Black Beauty/Bumblebee capacitor C710 whose leakage (likely, if not inevitable) will cause "350" to regulate low. Check if voltages make sense on the voltage divider R710,711,712. If the regulator is "working," V724 grid will be a volt or two below ground. Also maybe check D679 (reverse protection). You'll see BB caps used for all the regulator time constants, and all are suspect. C710 and C740 run close to rated voltage however, so other things equal, these might be the first to go. mike toggle quoted message Show quoted text --- In TekScopes@..., "yurighisio" <yurighisio@...> wrote: Hello, I have "only" problem with low voltage power supply, the crt circuit seems to be ok. Juri
Juri Ghisio Member Profile All Messages By This Member #77986 Hello, I have repaired the low voltage power supply, the problem was in a 6080 tube V737A. I have replaced this tube and voltage are ok. For future repair and check purpose, have anyone the current for each voltage ? I have performed calibration, it seem to work well. A strange problem appears on crt when the trace intensity increase, past the control middle point, trace thickens and glow down. I have checked -1700V and +8300V they don't change with knob moving, control grid voltage (pin 3) change accordingly with intensity control from -1900 to -1700. Juri
Merchison Burke All Messages By This Member #77998 开云体育 On TV sets, this is a sign of a bad CRT. On 2012-07-08 2:12 PM, yurighisio wrote: toggle quoted message Show quoted text Hello, I have repaired the low voltage power supply, the problem was in a 6080 tube V737A. I have replaced this tube and voltage are ok. For future repair and check purpose, have anyone the current for each voltage ? I have performed calibration, it seem to work well. A strange problem appears on crt when the trace intensity increase, past the control middle point, trace thickens and glow down. I have checked -1700V and +8300V they don't change with knob moving, control grid voltage (pin 3) change accordingly with intensity control from -1900 to -1700. Juri
ditter2 All Messages By This Member #78011 --- In TekScopes@..., Merchison Burke <merchison@...> wrote: On TV sets, this is a sign of a bad CRT. On 2012-07-08 2:12 PM, yurighisio wrote: Hello, I have repaired the low voltage power supply, the problem was in a 6080 tube V737A. I have replaced this tube and voltage are ok. For future repair and check purpose, have anyone the current for each voltage ? I have performed calibration, it seem to work well. A strange problem appears on crt when the trace intensity increase, past the control middle point, trace thickens and glow down. I have checked -1700V and +8300V they don't change with knob moving, control grid voltage (pin 3) change accordingly with intensity control from -1900 to -1700. Juri Yes, classic double peaking of the CRT cathode. It is very tired and has limited life remaining.

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