Fixing a legend.....
- Thread starter blu_fuz
- Start date
Ok but math doesn't lie. I'm not saying that your negative probe is not clipped at the correct location. What I am saying however is that if you are going to rely on that location as an anchor point to take measurements and you get a negative reading, then you need to immediately investigate that because ALL of your readings are based on that. The chassis is hanging, things are rubbing together, something conductive can be throwing your readings for a loop, whatever. No matter the reason, on a DC system, if your neg probe is clipped to ground and you produce a neg reading, then ground is not really at zero potential. It's simple math.
Alligator clip to ground coil spring in battery compartment:
Alligator clip to DMM ground probe:
My station with everything hooked up. No components touching each other. I put a mailing envelope between the tipped up board and the rest of the boombox to make sure nothing is touching. Also had to put the main board up on a box because the cables tethered to it don't have any slack whatsoever.
Here is the power supply board info:
View attachment 5350 Power Supply.pdf
View attachment 5350 Power Supply wire diagram.pdf
Alligator clip to DMM ground probe:
My station with everything hooked up. No components touching each other. I put a mailing envelope between the tipped up board and the rest of the boombox to make sure nothing is touching. Also had to put the main board up on a box because the cables tethered to it don't have any slack whatsoever.
Here is the power supply board info:
View attachment 5350 Power Supply.pdf
View attachment 5350 Power Supply wire diagram.pdf
Check this when you can. AC UNPLUGGED PLEASE for the resistance measurement. The reason is that transformer is live as soon as cord in plugged in REGARDLESS of power switch position.
Kudos to both of you for this tremendous effort. Please know that once this is done, it will go on file as a permanent guide for future endeavors.
Everyone should pay attention as this is how it is done when you have some masters to teach the students.
Everyone should pay attention as this is how it is done when you have some masters to teach the students.
Thanks everyone. Its harder to stay committed than I thought it would be. I would be really stuck if Norm hasn't been keeping up in this thread. Thanks buddy.
I know what you mean. Many times Norm has come to my rescue. Norm is just a straight forward guy and doesn't beat around the bush. I feel for ya Joe especially since I've been through it pulling my hair out just trying to find something wrong so I could repair issue. Patience is a virtue and something I have none of
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I know what you mean. Many times Norm has come to my rescue. Norm is just a straight forward guy and doesn't beat around the bush. I feel for ya Joe especially since I've been through it pulling my hair out just trying to find something wrong so I could repair issue. Patience is a virtue and something I have none of
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Joe. Just wondering. Have you inspected, metered out the function /power switch?
This is a very vulnerable and delicate leaf style switch and those leafs tend to loose their tension
And lead to bad contact. Power and line level current flow through that switch. So just a thought.
Would be nice if it were that simple.
Sorry if this has been brought up already as I haven't been following this thread every day.
This is a very vulnerable and delicate leaf style switch and those leafs tend to loose their tension
And lead to bad contact. Power and line level current flow through that switch. So just a thought.
Would be nice if it were that simple.
Sorry if this has been brought up already as I haven't been following this thread every day.
Results:Superduper said:Check this when you can. AC UNPLUGGED PLEASE for the resistance measurement. The reason is that transformer is live as soon as cord in plugged in REGARDLESS of power switch position.
blu_fuz_ps_measure.jpg
Power Off, no AC plug inserted - resistance from negative side of battery coil to solder pad/leg of D403 on PS board is 0.3 ohms.
Power on - voltage from negative side of battery coil to solder pad/leg of D403 on PS board is 0 volts.
Now, on the topic of finding a known good ground for my voltage tests. I put my DMM (-) probe on negative pad of CP206 (power/ground) to main board. I had good continuity to each "E" pad of Q408, Q108, and Q208 which were the components that had results of (-) voltage readings before. I checked each one of those components voltages again (Q408, Q108, Q208) with the CP206 known good ground and confirmed the negative voltage values I had gotten earlier.
I did another voltage test with my DMM (-) clamped to the battery spring negative coil and my (+) probe @ the line-in positive pad. The voltage reading was 0.012v, which I think confirms what you said about the negative battery spring is not properly grounded, correct? I don't know if that clears anything up or makes it more confusing
.IC403 (BA1355). This is the stereo decoder. Hopefully it is ok because it might be a little hard to find.
1) Check value of R420 = 4.7K Ω
R420 printed resistor is directly under IC403. So, testing from vias to vias across R420 was NO RESULT. No value shown in ohms reading. Because of no result I probed from pin 8 to pin 4 of IC403 (which is the next pad of each end of that section of circuit) again, no result on the meter for an ohms reading. Didn't even register when probing. Possible bad section of printed trace and printed resistor?
Q407: Check the following:
1) Resistance, R458 (lead opposite Q407-B) to S3-4 (pin 1 & 4), confirm = 100Ω
Results: 100Ω
2) Resistance, S3-4 (pin 1 & 4) to R441 (both pins), confirm R=0Ω & R=100Ω
Results: R=0.3Ω & R=100
3) Resistance, R441 (both leads) to Q206-C, confirm R=0Ω & R=100Ω
Results: R=0Ω & R=100
IC402: I would change it if I were you.
Currently waiting for this part to show up.
Q408: You marked it as if there was some anomoly in the readings. Yet, I don't see any test voltages marked.
Q408 readings are not penciled in on the schematic but are shown on the board diagram.
Q408:
C) 8.4v reading = -0.56v
B) 7.6v reading = 9.02v
E) 8.4v reading = 9.02v
Q411: Check:
1) Voltage, @ R464 (both sides)
Result: power on is 0v on both sides.
2) Resistance, R464 (both sides) to D103/D203 (the lead common to both diodes).
Result: Q411 pad "B" through R464 to common lead of D103/D203 = 4.07kΩ
R465: Check:
1) Resistance value
Result: 2kΩ
2) Continuity of the traces from the pins of R465 to at least 1 or 2 trace pads further up/down stream.
Result: CP203 @ #1 pin to R465 is good continuity.
1) Check value of R420 = 4.7K Ω
R420 printed resistor is directly under IC403. So, testing from vias to vias across R420 was NO RESULT. No value shown in ohms reading. Because of no result I probed from pin 8 to pin 4 of IC403 (which is the next pad of each end of that section of circuit) again, no result on the meter for an ohms reading. Didn't even register when probing. Possible bad section of printed trace and printed resistor?
Q407: Check the following:
1) Resistance, R458 (lead opposite Q407-B) to S3-4 (pin 1 & 4), confirm = 100Ω
Results: 100Ω
2) Resistance, S3-4 (pin 1 & 4) to R441 (both pins), confirm R=0Ω & R=100Ω
Results: R=0.3Ω & R=100
3) Resistance, R441 (both leads) to Q206-C, confirm R=0Ω & R=100Ω
Results: R=0Ω & R=100
IC402: I would change it if I were you.
Currently waiting for this part to show up.
Q408: You marked it as if there was some anomoly in the readings. Yet, I don't see any test voltages marked.
Q408 readings are not penciled in on the schematic but are shown on the board diagram.
Q408:
C) 8.4v reading = -0.56v
B) 7.6v reading = 9.02v
E) 8.4v reading = 9.02v
Q411: Check:
1) Voltage, @ R464 (both sides)
Result: power on is 0v on both sides.
2) Resistance, R464 (both sides) to D103/D203 (the lead common to both diodes).
Result: Q411 pad "B" through R464 to common lead of D103/D203 = 4.07kΩ
R465: Check:
1) Resistance value
Result: 2kΩ
2) Continuity of the traces from the pins of R465 to at least 1 or 2 trace pads further up/down stream.
Result: CP203 @ #1 pin to R465 is good continuity.
Joe:
I've been going back forth on some of these measurements and flipping back/forth between your readings and the diagram, I might get lost and so these recommendations are somewhat random. Anyhow, rather than 15 back/forth step by steps, I'm going to trust you to do a little diagnostics along the way with some guidance.
Q411: Base leg needs .7 volts to be switched ON. Until it's switched on, the voltage at Q108/Q208/Q408 will be wrong. You need to follow the diagram (use schematic) and find out why you aren't getting at least some voltage. D103/D203 is getting .7volts and it's also tethered to (a) jumper (like Q411) so you'll have to figure out where the issue is. Also make absolutely sure that you did not accidently ground that circuit when you made all those jumper bridges (in case they were jumped wrong).
Q109, Q209, Q407: I believe all of these transistors are not turning on due to an issue with the circuit feeding it. Follow along with me.... You said previously that Q206-C is getting ~7.5v, right? This is about right. Now from there, follow the circuit through this path:
Q206-C --> R441 --> (S3-4 pin 4) --> (S3-4 pin 1) --> (S2-12 pin2) --> (S2-12 pin1) --> R468 --> [C jumper]
From [C-jumper], the circuit goes through R458 to Q407-B and also from [C-jumper], goes through R465 to Q109/Q209. None of these transistors are getting voltage at the base, but since you are getting 7.5v at C-Q206, there obviously is a break somewhere. You need to follow and find the break.
IC403: I don't have an internal block diagram so can't comment on the innards and any effect it would have on those pins. However, it looks to me like R420 is toast. I would cut the trace to R420 to take it out of circuit, then tack a discrete 4.7k resistor between pins 4-6 or 4-8, whichever is easier, from the foil side. Also, if the trace area around R420 shows any sign of corossion, you should check continuity between all.
One comment of note: Please use correct language when expressing measurements. NO RESULT is NOT proper way of expressing measurements and leads to misunderstandings and confusion. Does no result mean "0"? Or does it mean infinity? I am presuming you mean infinity. However, you should always express such readings as infinity or OC (open circuit). 0 is 0, 100 is 100 and infinity is OC, but no-result means whatever the person interpreting it means. In other words, when taking a measurement, there is ALWAYS A RESULT.
I've been going back forth on some of these measurements and flipping back/forth between your readings and the diagram, I might get lost and so these recommendations are somewhat random. Anyhow, rather than 15 back/forth step by steps, I'm going to trust you to do a little diagnostics along the way with some guidance.
Q411: Base leg needs .7 volts to be switched ON. Until it's switched on, the voltage at Q108/Q208/Q408 will be wrong. You need to follow the diagram (use schematic) and find out why you aren't getting at least some voltage. D103/D203 is getting .7volts and it's also tethered to (a) jumper (like Q411) so you'll have to figure out where the issue is. Also make absolutely sure that you did not accidently ground that circuit when you made all those jumper bridges (in case they were jumped wrong).
Q109, Q209, Q407: I believe all of these transistors are not turning on due to an issue with the circuit feeding it. Follow along with me.... You said previously that Q206-C is getting ~7.5v, right? This is about right. Now from there, follow the circuit through this path:
Q206-C --> R441 --> (S3-4 pin 4) --> (S3-4 pin 1) --> (S2-12 pin2) --> (S2-12 pin1) --> R468 --> [C jumper]
From [C-jumper], the circuit goes through R458 to Q407-B and also from [C-jumper], goes through R465 to Q109/Q209. None of these transistors are getting voltage at the base, but since you are getting 7.5v at C-Q206, there obviously is a break somewhere. You need to follow and find the break.
IC403: I don't have an internal block diagram so can't comment on the innards and any effect it would have on those pins. However, it looks to me like R420 is toast. I would cut the trace to R420 to take it out of circuit, then tack a discrete 4.7k resistor between pins 4-6 or 4-8, whichever is easier, from the foil side. Also, if the trace area around R420 shows any sign of corossion, you should check continuity between all.
One comment of note: Please use correct language when expressing measurements. NO RESULT is NOT proper way of expressing measurements and leads to misunderstandings and confusion. Does no result mean "0"? Or does it mean infinity? I am presuming you mean infinity. However, you should always express such readings as infinity or OC (open circuit). 0 is 0, 100 is 100 and infinity is OC, but no-result means whatever the person interpreting it means. In other words, when taking a measurement, there is ALWAYS A RESULT.
Some progress.
IC402:
Removed original IC402 and replaced with brand new IC. Voltage readings are the same with the new part as with the old.
IC403:
Cut printed trace of R420. Added 4.7k resistor to bridge pins 4 and 8 of IC403. Voltage readings are now restored to factory spec for IC403.
Q206-C --> R441 (Q206-C, through R441, to S3-4 pin 4 should be 100k, measured 100k) --> (S3-4 pin 4) (continuity between pin 4 and pin 1 on S3-4 when function switch flipped on to radio) --> (S3-4 pin 1) (continuity between S3-4 pin 1 to S2-12 pin 2) --> (S2-12 pin2) --> (S2-12 pin1) (S2-12 pin 1, through R468, to beginning and after C-jumper should be 100k, measured 100k) --> R468 --> [C jumper]
From [C-jumper], the circuit goes through R458 to Q407-B (from C-jumper, through R458, to Q407 should be 100k, measured 91.4k) and also from [C-jumper], goes through R465 to Q109/Q209. (from C-jumper, through R458 to Q109/Q209 should be 2.2k, measured 2k)
^ From what I can tell from start to finish of the Q206 notes above, I had continuity and restance readings within spec throughout those circuits.
Q411:
I need to take more time and look this area over good and do more tests.
IC402:
Removed original IC402 and replaced with brand new IC. Voltage readings are the same with the new part as with the old.
IC403:
Cut printed trace of R420. Added 4.7k resistor to bridge pins 4 and 8 of IC403. Voltage readings are now restored to factory spec for IC403.
Q206-C --> R441 (Q206-C, through R441, to S3-4 pin 4 should be 100k, measured 100k) --> (S3-4 pin 4) (continuity between pin 4 and pin 1 on S3-4 when function switch flipped on to radio) --> (S3-4 pin 1) (continuity between S3-4 pin 1 to S2-12 pin 2) --> (S2-12 pin2) --> (S2-12 pin1) (S2-12 pin 1, through R468, to beginning and after C-jumper should be 100k, measured 100k) --> R468 --> [C jumper]
From [C-jumper], the circuit goes through R458 to Q407-B (from C-jumper, through R458, to Q407 should be 100k, measured 91.4k) and also from [C-jumper], goes through R465 to Q109/Q209. (from C-jumper, through R458 to Q109/Q209 should be 2.2k, measured 2k)
^ From what I can tell from start to finish of the Q206 notes above, I had continuity and restance readings within spec throughout those circuits.
Q411:
I need to take more time and look this area over good and do more tests.
