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Post by mastertech on Jun 17, 2022 14:54:41 GMT -5
If you look at the schematic for the "Primary Unit" mini power supply, you will see where the main transformer connects to that board at W791 and W792. Can you disconnect those wires and try powering it up again and see if the smell is still there or gone?
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 17, 2022 18:41:23 GMT -5
 ahhmmm.. I think I'm into something here. This TR607 which is an A988 on the board 1U-3295. This has no junction from base to collector. I think it is open, there are 3 transistor near it with the same component number (A988), and this one differs from both. I basically just followed the smell. lol . Removed the DSP board smelled the back side but there was nothing, smelled the board next to it, as this has about 3 layers stack on top of the other. Smell was there, tried a magnifying glass to check for cold solders, nothing. Checked the diodes, all good. Until I came to this specific tranny, and now this. Could this one cause all this mess up? ---- man talking about false hopes.... didn't realize it tell now, collector and base is shunted, thus the no junction.. lol .. off to next target.. |
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 17, 2022 20:07:55 GMT -5
If you look at the schematic for the "Primary Unit" mini power supply, you will see where the main transformer connects to that board at W791 and W792. Can you disconnect those wires and try powering it up again and see if the smell is still there or gone? I disconnected W791 and W792, all other boards connected, only W791 and W792 were disconnected, turned switch S801, 1-5 to ON, some of the other relays that previously clicked were not clicking. I guess those relays was for the main amp. Smell and smoke is gone. Looks like this is going to the main transformer. As what I've said previously, I tried smelling the boards, I previously thought it was the second board as there was a stronger smell there, but after smelling the transformer, a much stronger smell is there. Looks like it "transformer" section is where this smell is coming from. This is s toroidal transformer. Here are some of the measurements I did. These measurements are the same with Switch 801 either ON or OFF position. on IC802, Pin 10 - 5V ~ 4.8V Pin 44 - 4.33V Pin 45 - 43 mV on CX073 Pin 1 - 3 - 1.275V Pin 4 - 3 - 566mV Pin 2 - 3 - -17.6mV |
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Post by mastertech on Jun 17, 2022 21:18:48 GMT -5
If you look at the schematic for the "Primary Unit" mini power supply, you will see where the main transformer connects to that board at W791 and W792. Can you disconnect those wires and try powering it up again and see if the smell is still there or gone? I disconnected W791 and W792, all other boards connected, only W791 and W792 were disconnected, turned switch S801, 1-5 to ON, some of the other relays that previously clicked were not clicking. I guess those relays was for the main amp. Smell and smoke is gone. Looks like this is going to the main transformer. As what I've said previously, I tried smelling the boards, I previously thought it was the second board as there was a stronger smell there, but after smelling the transformer, a much stronger smell is there. Looks like it "transformer" section is where this smell is coming from. This is s toroidal transformer. Here are some of the measurements I did. These measurements are the same with Switch 801 either ON or OFF position. on IC802, Pin 10 - 5V ~ 4.8V Pin 44 - 4.33V Pin 45 - 43 mV on CX073 Pin 1 - 3 - 1.275V Pin 4 - 3 - 566mV Pin 2 - 3 - -17.6mV Ok, so now we have something that does not look right. When S801, switch 5-1 is switched on you should have higher voltage on ic802 pin 45 and CX073 pin 1. These 2 locations should also be the same voltage. Test again but use chassis for ground probe just to see. If no change then locate R840. Should be near ic801. Check to see if the voltage is the same on both sides. Use chassis for ground probe. As a matter of fact, do a continuity test between chassis case and pin 3 of CX073 just to see if they are connected for testing purposes. |
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 17, 2022 22:28:17 GMT -5
I disconnected W791 and W792, all other boards connected, only W791 and W792 were disconnected, turned switch S801, 1-5 to ON, some of the other relays that previously clicked were not clicking. I guess those relays was for the main amp. Smell and smoke is gone. Looks like this is going to the main transformer. As what I've said previously, I tried smelling the boards, I previously thought it was the second board as there was a stronger smell there, but after smelling the transformer, a much stronger smell is there. Looks like it "transformer" section is where this smell is coming from. This is s toroidal transformer. Here are some of the measurements I did. These measurements are the same with Switch 801 either ON or OFF position. on IC802, Pin 10 - 5V ~ 4.8V Pin 44 - 4.33V Pin 45 - 43 mV on CX073 Pin 1 - 3 - 1.275V Pin 4 - 3 - 566mV Pin 2 - 3 - -17.6mV Ok, so now we have something that does not look right. When S801, switch 5-1 is switched on you should have higher voltage on ic802 pin 45 and CX073 pin 1. These 2 locations should also be the same voltage. Test again but use chassis for ground probe just to see. If no change then locate R840. Should be near ic801. Check to see if the voltage is the same on both sides. Use chassis for ground probe. As a matter of fact, do a continuity test between chassis case and pin 3 of CX073 just to see if they are connected for testing purposes. Here goes: Continuity test - chassis to pin 3 of CX073 - no continuity... no connection.. IC802 Pin 45 to chassis S801: (pin 1-5) OFF - 525mV ON - 782mV CX073 Pin 1 to chassis S801: (pin 1-5) OFF - -520mV ON - 809mV R840 Pin 1 (CY073) side S801: (pin 1-5) OFF - -523mV ON - 800mV Pin 1 (S801) side S801: (pin 1-5) OFF - -180mV ON - 5V |
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Post by mastertech on Jun 18, 2022 10:14:04 GMT -5
Can you disconnect the harness at CY073 and recheck the voltages on both sides of R840?
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 18, 2022 11:58:27 GMT -5
I did an ohms test on the power amp transformer, the one where I disconnected the W791 and W792. It is 0.5ohms, pretty much tells me it is shorted at the primary side.  |
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 18, 2022 12:05:31 GMT -5
Can you disconnect the harness at CY073 and recheck the voltages on both sides of R840? On R840 with harness at CY073 disconnected - I can't measure directly from the Resistor as it is on the back side of the board, and if I where to get to it, I would have to disconnect all the other harnesses, so I'm getting the voltages that are directly connected to it on both sides. Also, I did ohms test of the pins. It is at approx 7k ohms, schematic would say 10k but I'd guess it is acceptable in-circuit measurement. With harness at CY073 disconnected here are the measurements. With S801 ON: Pin 1 (CY073) - 3.8V Pin 1 (S801) - 4.64V With S801 OFF: Pin 1 (CY073) - -481.6mV Pin 1 (S801) - -481mV |
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Post by mastertech on Jun 18, 2022 13:22:15 GMT -5
I did an ohms test on the power amp transformer, the one where I disconnected the W791 and W792. It is 0.5ohms, pretty much tells me it is shorted at the primary side. Actually this reading indicates the transformer is probably ok. Plus I was not thinking the transformer was a problem anyways. I only had you disconnect it to prevent many other components from getting power in an attempt to narrow down what is causing the smoke and smell. |
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Post by mastertech on Jun 18, 2022 13:27:29 GMT -5
Ok, looks like the voltage came up on CY073 so we appear to have a problem on the primary unit (mini power supply).
On the power supply, can you do an ohm test on CX073 across pins 1 and 3
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 18, 2022 19:43:14 GMT -5
Ok, looks like the voltage came up on CY073 so we appear to have a problem on the primary unit (mini power supply). On the power supply, can you do an ohm test on CX073 across pins 1 and 3 In the mini transformer, wires from the mains are directly connected to the minitransformer, an ohms test on the terminals will give about 90 ~ 100ohms reading. An ohms test on the - Amp Transformer gives close to 0 ohms - I have them disconnected, also according to the schematic those wires are directly going to the mains of the amp transformer. I'm just wondering why you think amp transformer is good? |
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 18, 2022 19:43:48 GMT -5
Ok, looks like the voltage came up on CY073 so we appear to have a problem on the primary unit (mini power supply). On the power supply, can you do an ohm test on CX073 across pins 1 and 3 CX073 this harness goes to CY073, It is 7.5Kohms - disconnected, and 5.5kOhms when the harness is connected. |
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Post by mastertech on Jun 18, 2022 20:00:02 GMT -5
Ok, looks like the voltage came up on CY073 so we appear to have a problem on the primary unit (mini power supply). On the power supply, can you do an ohm test on CX073 across pins 1 and 3 In the mini transformer, wires from the mains are directly connected to the minitransformer, an ohms test on the terminals will give about 90 ~ 100ohms reading. An ohms test on the - Amp Transformer gives close to 0 ohms - I have them disconnected, also according to the schematic those wires are directly going to the mains of the amp transformer. I'm just wondering why you think amp transformer is good? The short answer is: not all transformers have the same resistance. The resistance is based on the number of turns and the gauge of wire. Testing resistance on a transformer will not determine if it is bad or not unless the reading is open. A shorted transformer must be tested differently and I do not believe we are there yet. Other problems must be determined first which is what we are trying to do. |
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Post by mastertech on Jun 18, 2022 20:05:49 GMT -5
Ok, looks like the voltage came up on CY073 so we appear to have a problem on the primary unit (mini power supply). On the power supply, can you do an ohm test on CX073 across pins 1 and 3 CX073 this harness goes to CY073, It is 7.5Kohms - disconnected, and 5.5kOhms when the harness is connected. I am aware of where this harness goes. And I have no idea of what your test here is. Harness connected or not. So let me try to explain the test I need differently. Go to the "Primary Unit board". Disconnect harness at CX073. Set meter to ohm scale. Put on probe on pin 1 inside CX073 connector and the other probe on pin 3 inside CX073 connector and give me the reading. |
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nodols
Junior Member
Posts: 75
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Post by nodols on Jun 18, 2022 20:42:41 GMT -5
CX073 this harness goes to CY073, It is 7.5Kohms - disconnected, and 5.5kOhms when the harness is connected. I am aware of where this harness goes. And I have no idea of what your test here is. Harness connected or not. So let me try to explain the test I need differently. Go to the "Primary Unit board". Disconnect harness at CX073. Set meter to ohm scale. Put on probe on pin 1 inside CX073 connector and the other probe on pin 3 inside CX073 connector and give me the reading. Hey sorry, I should have mentioned the pins. Yup, those readings are from pins 1 and 3 of CX073 The 7.5kohms is when I disconnected one side of the harness from CY to CX073 , when I have it connected both sides, it is 5.5kohms. |
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