Ok, I see.
I see the multifunction test indicates that TR705 is good but the EC reading of .35 / .39 indicates a short.
Try to measure the voltages at the crosspoint of D702 and VR711 and try to find out why you have no voltage at collector of TR705. It should be 24V.
I see the multifunction test indicates that TR705 is good but the EC reading of .35 / .39 indicates a short.
Try to measure the voltages at the crosspoint of D702 and VR711 and try to find out why you have no voltage at collector of TR705. It should be 24V.
Hi knockbill,
The lamp lights, then goes off - correct?
Germanium transistors have high leakage, and also high beta. The base - emitter drop is very low as well. Hugo's suggestion for the AC151 is good, but you may not need a new transistor. It is rare for a transistor to work, then not, and then work again.
Most diode testers these days don't measure germanium junctions well, and may react to a higher leakage current. I only trust very good meters. Some pass about 1 mA through the junction on diode test and read the voltage drop. I think Fluke does, HP / Agilent / Keysight does for sure. You can do this yourself by using an 8K2 resistor and 9 V battery and just measure the voltage drop. Expect 0.2 ~ 0.3 V across your part junctions.
When you use a sub book, always check the original specs for each part! They do make mistakes, and also check the pin-out for the leads and case style. If you ever use an NTE or ECG replacement manual, be aware they are known as "the book of lies". Also, never find a cross reference, then cross reference to that. That's a sure way to get the wrong part.
Use a good, zero -residue cleaner on your function switch. That may well solve some issues. If you spray it with anything else, you'll have to clean it again with a zero residue cleaner. Take care you don't wash out the lubricants on the shaft. For pots (controls) use as little as possible. Cleaners (all) attack the lubricants inside, and it is not the carbon track that is noisy.
The lamp lights, then goes off - correct?
Germanium transistors have high leakage, and also high beta. The base - emitter drop is very low as well. Hugo's suggestion for the AC151 is good, but you may not need a new transistor. It is rare for a transistor to work, then not, and then work again.
Most diode testers these days don't measure germanium junctions well, and may react to a higher leakage current. I only trust very good meters. Some pass about 1 mA through the junction on diode test and read the voltage drop. I think Fluke does, HP / Agilent / Keysight does for sure. You can do this yourself by using an 8K2 resistor and 9 V battery and just measure the voltage drop. Expect 0.2 ~ 0.3 V across your part junctions.
When you use a sub book, always check the original specs for each part! They do make mistakes, and also check the pin-out for the leads and case style. If you ever use an NTE or ECG replacement manual, be aware they are known as "the book of lies". Also, never find a cross reference, then cross reference to that. That's a sure way to get the wrong part.
Use a good, zero -residue cleaner on your function switch. That may well solve some issues. If you spray it with anything else, you'll have to clean it again with a zero residue cleaner. Take care you don't wash out the lubricants on the shaft. For pots (controls) use as little as possible. Cleaners (all) attack the lubricants inside, and it is not the carbon track that is noisy.
OK, thanks,,,
I tried to measure Voltage from junction of D702 and VR711,,, it ranged from 20V to 45+VDC,, making static in the Left(bad side) speakers, so I shut it down,,, there isn't a load on that side with TR705 out of the circuit, tho...
Maybe I should wait until the transistors get here, probably in a couple hours,,, and try again??
I dont want to do more damage to it!!!!
I tried to measure Voltage from junction of D702 and VR711,,, it ranged from 20V to 45+VDC,, making static in the Left(bad side) speakers, so I shut it down,,, there isn't a load on that side with TR705 out of the circuit, tho...
Maybe I should wait until the transistors get here, probably in a couple hours,,, and try again??
I dont want to do more damage to it!!!!
All good points from Anatech! The AC151 will be a replacement for TR503 (2SB54) who is most probably broken.
Unfortunately AC151 is hard to find and I had a AC187 wich is on his way to John.
If there is 20 - 45V on VR711, there is either a broken track or a bad soldering at the collector of TR705.
Take it easy with the new transistors.
Unfortunately AC151 is hard to find and I had a AC187 wich is on his way to John.
If there is 20 - 45V on VR711, there is either a broken track or a bad soldering at the collector of TR705.
Take it easy with the new transistors.
"You can do this yourself by using an 8K2 resistor and 9 V battery and just measure the voltage drop. Expect 0.2 ~ 0.3 V across your part junctions."
Thanks for replying,,, bias problem is priority now, as I can't run the amp til its sorted,,, Not sure how this works,, do you have a schematic for teh DIY tester?
I've used CRC contact cleaner for switches for many years,, seems to do the job,,, and always put a drop of oil on a shaft bushing after cleaning...
I appreciate your input!
Thanks for replying,,, bias problem is priority now, as I can't run the amp til its sorted,,, Not sure how this works,, do you have a schematic for teh DIY tester?
I've used CRC contact cleaner for switches for many years,, seems to do the job,,, and always put a drop of oil on a shaft bushing after cleaning...
I appreciate your input!
Will do, I will need to replace TR705, using one of the subs I have in for TR701and 703.... The new trans are for TR 701-704,,,
This will be like starting over,,, DBT and variac til it measures correctly,,, Big mistake I made was not checking bias after I got it running,,, but until you replied I was dancing with myself!!!! I do believe I had it close before and either a solder joint gave out or other trace problem happened while I was moving it around for access... Eyesight is always a factor!!!!
I wont mess with the indicator light or FM/MPX til the amp is right,,,
And I truly thank all that are offering help/info,,, this would be on the shelf without you!!!!
I'll get back to it as soon as the new transistors arrive...
Speaking of the new transistors,, I ordered some KSC1815 as replacements for 2SC536 (TR701~704).... KSC1815 are recommended replacements,,, but my research indicates their frequency is only 80MHz,, opposed to 115MHz for the 2SC536s,,,,
I was told it would not be an issue as the subs will be fast enough for the ckts they will used in....
Does anyone think they will be a problem??? If it's not recommended here,,, I can use the 2N3904's which exceed all the 536 ratings...
Thanks again for the info,,,
I was told it would not be an issue as the subs will be fast enough for the ckts they will used in....
Does anyone think they will be a problem??? If it's not recommended here,,, I can use the 2N3904's which exceed all the 536 ratings...
Thanks again for the info,,,
I finally got the bad side "temporary" transistors replaced,,, biased and hopefully working fine,,, but time will tell.... I used the KSC1815s for the 2SC536s,,, and moved a 2N2222 trans I used as a temp, for the corroded TR401-403,, in for the questionable TR405.... Reflowed a lot of joints, any that looked suspicious,,, and played it while.... Seems like it's holding bias OK,,, but time will tell....
A humble thanks to Hugo and the others who contributed so far,,, we're far from finished but amp least the amp/preamp stages seems to work!!!
A humble thanks to Hugo and the others who contributed so far,,, we're far from finished but amp least the amp/preamp stages seems to work!!!
Right back at you !!! I may have sorted it out sooner or later,,, but your help made it happen a lot quicker!!!! I think I'll replace any more transistors that have that corrosion on the pins,,, I have at least one more,,, After I'm sure bias is stable,, I'll look at The FM problem again, an dlookinto the tester Anatech suggested,,, I thought I saw a schematic for something like that, but will have to find it again...
Its coming along slowly!!!
Its coming along slowly!!!
I've been studying the schematic,,, I can't understand how the lamp not working because of a problem on the TRI-A1 Board will keep the stereo signal from splitting on the TRX-6 (MPX) board, and coming out as two signals(4H and 4G),,, I can't see how the signal coming out of TRF-2BA goes thru TRI-A1, as it appears to be a driver ckt, just tapped off TRX-6 for the lamp?
Just thinking about what Anatech wrote about a transistor working intermittently,,, as the lamp lights a few seconds when FM is selected, and the FM ckt has been off a while, but not long enough to listen for stereo.....
But I will wait for the transistor (TR503), from Hugo,, and try that first !!!
Just thinking about what Anatech wrote about a transistor working intermittently,,, as the lamp lights a few seconds when FM is selected, and the FM ckt has been off a while, but not long enough to listen for stereo.....
But I will wait for the transistor (TR503), from Hugo,, and try that first !!!
Just an update,,, TR503 replacement arrived from Hugo, but it had a rough trip!! the PO here damaged the package,,, and the transistor, doesn't read good,,,
I am still contemplating installing it to try,, but further testing and measuring values, shows there is no MPX, even tho FM comes in pretty strong... So the FM indicator light shouldn't be working!!!!
So far I've replaced the 4 small transistors(TR404~407) on the MPX board,, and tested the Ge trans (TR40~403) that are left and they test to schem voltage... Also tested all the diodes on the board, all are good....
I can read 19kHz after D401-2,, but can't get 38kHz after TR403,, or TP 4G-4H... I found the borrowed scope I have has an iffy channel two, so I was taking frequency readings with channel one....
Bottom line,, there is no stereo coming thru FM/MPX only mono, which doesn't change with stereo/mono switch...
AUX inputs with CDP have good, balanced stereo output...
Thanks for Netlists help in getting this far!!!!
I am still contemplating installing it to try,, but further testing and measuring values, shows there is no MPX, even tho FM comes in pretty strong... So the FM indicator light shouldn't be working!!!!
So far I've replaced the 4 small transistors(TR404~407) on the MPX board,, and tested the Ge trans (TR40~403) that are left and they test to schem voltage... Also tested all the diodes on the board, all are good....
I can read 19kHz after D401-2,, but can't get 38kHz after TR403,, or TP 4G-4H... I found the borrowed scope I have has an iffy channel two, so I was taking frequency readings with channel one....
Bottom line,, there is no stereo coming thru FM/MPX only mono, which doesn't change with stereo/mono switch...
AUX inputs with CDP have good, balanced stereo output...
Thanks for Netlists help in getting this far!!!!
Update,,,
I finally found a good, NOS sub for TR503, put it in this morning,, and get the same results as I did from the original 2SB54,, light comes on momentarily when a strong station is tuned but fades out in less than 10 seconds... Problem has to be on the FM MPX board,, not sure how to trouble shoot from here...
I finally found a good, NOS sub for TR503, put it in this morning,, and get the same results as I did from the original 2SB54,, light comes on momentarily when a strong station is tuned but fades out in less than 10 seconds... Problem has to be on the FM MPX board,, not sure how to trouble shoot from here...
Hi knockbill,
Yes, the MPX board / circuit is where to look.
You need a stereo FM signal generator and an oscilloscope at the minimum to alight the MPX. Also some non-ferrous tools to adjust coils without throwing them off or cracking the cores. If you crack a core you are in real trouble. You can do this using the wrong tool, or if the core is too "sticky" or jammed.
I wouldn't advise trying this without the right tools and experience.
-Chris
Yes, the MPX board / circuit is where to look.
You need a stereo FM signal generator and an oscilloscope at the minimum to alight the MPX. Also some non-ferrous tools to adjust coils without throwing them off or cracking the cores. If you crack a core you are in real trouble. You can do this using the wrong tool, or if the core is too "sticky" or jammed.
I wouldn't advise trying this without the right tools and experience.
-Chris
Hi,,
Thanks for replying!!!
Did you see post #95, That's where I left off waiting to get the sub for TR503... I think have sorted the scope, and I my buddy has a signal generator that will work,,, Experience is why I'm here!!!! I watched a couple Sansui alignment videos, and they are pretty intensive,,, but I got this far with Netlists help, so worse I can do is just have FM mono,,, the amp/AM/phono sections sound great!!!!
I appreciate your info!!!
Thanks for replying!!!
Did you see post #95, That's where I left off waiting to get the sub for TR503... I think have sorted the scope, and I my buddy has a signal generator that will work,,, Experience is why I'm here!!!! I watched a couple Sansui alignment videos, and they are pretty intensive,,, but I got this far with Netlists help, so worse I can do is just have FM mono,,, the amp/AM/phono sections sound great!!!!
I appreciate your info!!!
Hi knockbill,
Well, if you have access to the proper equipment, I'll assume that person also knows how to use it.
Okay, so you have 19 KHz at the collector of TR402 and also the two 1N60 (D401, 402) diodes. Check the base of TR403 for 38 KHz. Measure also the voltages on each terminal of TR403. If C413 goes open it might kill your 38 KHZ, C411 shorting would force you into mono. If C410 is a polystyrene type, check it for shorts. If it is, put the same type EXACTLY back in. Those capacitors are heat sensitive, but very stable and have excellent dielectric properties. C412 going open would probably reduce the amplitude, I'm not sure if it might kill the signal or not.
Hopefully that helps you.
Well, if you have access to the proper equipment, I'll assume that person also knows how to use it.
Okay, so you have 19 KHz at the collector of TR402 and also the two 1N60 (D401, 402) diodes. Check the base of TR403 for 38 KHz. Measure also the voltages on each terminal of TR403. If C413 goes open it might kill your 38 KHZ, C411 shorting would force you into mono. If C410 is a polystyrene type, check it for shorts. If it is, put the same type EXACTLY back in. Those capacitors are heat sensitive, but very stable and have excellent dielectric properties. C412 going open would probably reduce the amplitude, I'm not sure if it might kill the signal or not.
Hopefully that helps you.
I was playing the receiver today and went from Aux to FM and the MPX light came on when I tuned a station... It stayed on when station was tuned strong, and went out when it wasn't (according to the meter)... It did the same thing up and down the dial,, but there is a bit of noise and distortion in the back ground,, its not as clear as the other Sansui (800) I have...
This is set up in the the basement, on a crappy rabbit ears antenna, and the noise kind of sounds like a radio that's not tuned in well...
I'm going to try either running a cable to an outside antenna, or bringing the receiver upstairs.. It can't be as simple as this, can it???? Maybe the original transistor was weak or leaking, as it didn't match the schem voltages...
I'm getting the light to come on, but not sure its in stereo,,, maybe I need to adjust the separation pot on the back of the receiver...
I'll try an antenna outside,,, or try to set it up upstairs tomorrow,,, and I will check the parts you mentioned...
C410 is a mica,,, C411 is Mylar and C412 is a lytic, (if it matters) according to the parts list in the manual,,,
Thanks for the info...
This is set up in the the basement, on a crappy rabbit ears antenna, and the noise kind of sounds like a radio that's not tuned in well...
I'm going to try either running a cable to an outside antenna, or bringing the receiver upstairs.. It can't be as simple as this, can it???? Maybe the original transistor was weak or leaking, as it didn't match the schem voltages...
I'm getting the light to come on, but not sure its in stereo,,, maybe I need to adjust the separation pot on the back of the receiver...
I'll try an antenna outside,,, or try to set it up upstairs tomorrow,,, and I will check the parts you mentioned...
C410 is a mica,,, C411 is Mylar and C412 is a lytic, (if it matters) according to the parts list in the manual,,,
Thanks for the info...