Nnno... I wouldn't want to disassemble it that far. I fear I might end up with two inoperative units. ๐
it is safer for me to buy a few of those transistors and see if they would change anything in the faulty unit. ๐...
UserXP
Badcaps Veteran
Last Activity: Today, 01:23 PM
Joined: 04-14-2012
Location: Niลก, Serbia
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Thank you, all. Yes, I found a list of substitutes/equivalents of certain phased out components. While we were troubleshooting the low voltage issue, I found replacements for Q5-Q7, having the idea of changing them back then to see what would happen. There is a local electronics shop where I live and their website actually offers an available substitute part for the item searched. So finding a replacement locally isn't impossible.
I can buy some and try with Q1 first as it is easy to remove. I really hope it won't be in vain like with other unsoldered original components that turned out...Leave a comment:
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Thanks, Stj and CapLeaker. So, you don't think it's Q2. But, if I am to remove it and it turns out to be bad, I'd have to have a replacement part as there is no point in swapping them as I'd be still left with a faulty one in the circuit... Removing Q2 is something I don't how I'll manage to do. It is immersed in some kind of hardened paste. Can I buy a few 2SC930 transistors and just put the leads of the new one onto the pads where the existing Q2 is soldered? If the old one was bad, would the new one in parallel "take over"? This would save me the trouble of actually removing Q2 if...Last edited by UserXP; Today, 02:18 AM.Leave a comment:
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CapLeaker, OK, I checked L1, it is OK. I also reflowed the solder points on T3. It didn't make a difference. I also tried touching different solder point pads. Touching Q2's pins caused to switch to a near station frequency.
This is getting tedious... ๐
Hmmm... here is a thought; provided nobody messed with the trimmers and pots on the board... is it possible that replacing the capacitors alone has somehow influenced the alignment, maybe due to different resistance of the new caps or current flow or whatever?
I haven't discarded the old caps. Most of the small ones...Last edited by UserXP; Yesterday, 05:28 PM.Leave a comment:
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Will do. In the meantime, I did some additional checking on the working unit. Visually, it is identical, except it has original capacitors. But, I removed the tunning drum wheel. There are two small capacitors soldered onto the board. The faulty unit doesn't have those. I took a picture.
Then, I unsoldered its antenna wire. The working unit was still receiving radio signal at almost the same strength as with the antenna wire soldered. The faulty unit can't do that.
The main voltage is 13.3-14.8 volts DC, slightly lower than on the faulty unit. But the volume is crisp and prominent...Leave a comment:
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I checked the IF voltages on the IC01 of the working unit. Everything is almost the same, except I got 4.3V readings on pins 6 and 7, whereas on the faulty unit it was 4.5. Other voltages differ in 0.0X volts. Another dead end. ๐Leave a comment:
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It's not C24. I put a new 103 cap and there was no difference. ๐
So far, if we don't count the bad electrolytic capacitors, every other original Sony component I desoldered and tested turned out fine.Leave a comment:
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Ignore the previous test, the original antenna wire provides the most stable reception, so I using ut now (the volume is still low).
also, I removed C24. It measures 10.0nF, but it took like almost two seconds to reach the value in gradual increments, and then it stabilized. Without this cap, no sound is produced.
Can I temporarily introduce a different cap of this type and see how it affects the volume (if it would), or does the test reveal that C24 is actually fine?Last edited by UserXP; Yesterday, 03:54 AM.Leave a comment:
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I tested VD1220 and I would say it is OK. It has a 1.16V drop, but that is within its specs (1.12-1.20V). Plus, while it was removed from the circuit, there was no sound in either mode. So it is safe to assume that if it provides normal volume for AM, then it should do the same for FM.
Now, D5 has a 0.38 voltage drop, and D6 0.37. So, that's another dead end, I guess.
R12 measures 0.97K and it really is a 1k resistor, even though the manual suggests a 2.1K one here.
Now, I attached a probe with a clip to the ANT pad to serve as an antenna. The volume increases, BUT, even...Last edited by UserXP; Yesterday, 01:43 AM.Leave a comment:
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I couldn't find the reating in the manual, but CF seems to be an E10.7A filter and has a red dot on one corner. It also has some symbols below its value symbol, I can't see them well, but they might be manufacturer logos or so.
I found that this is likely a 10.7MHz ceramic filter. What do you think, should I try and find a replacement and see if it will have any impact?...Leave a comment:
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Naaah... You have been awesome. ๐...Leave a comment:
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Oh... shoot. In that case, I'm stuck. Before I started this topic, I actually called a few local repair shops in my town to ask if I can bring the radio to them to have a look at the problem. All of them said "We don't do that, we don't fix eletronics that old". I guess they got used to to microprocessors, chips, "all-in-one" circuits and what not. Old-school electronics repairman is impossible to find.
So, I tried my luck here and all of you people who stepped in and guided the noob me through all we have done, ant that is really amazing. From a non-working radio and...Leave a comment:
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This is great informative stuff, thanks a lot! Sure, I won't rush, we can wait for other input. Thanks to all of you, we have fixed several issues so far, this is the last one. Provided I can find a replacement CF, it wouldn't be too difficult the replace.
All the components are properly soldered, tinned and then soldered with a fresh solder blob. That C23 capacitor is 16V10Uf.
In circuit, R18 reads 2.17K.
C24 varies between 4.4 and 5.8mF in circuit. It is a round, green, flat capacitor....Leave a comment:
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OK, guys, thanks so much for the input. I have done the following measurements:
In AM mode, I'd say the voltages are closer to those reference voltages in the manual: Pin1=3.62V
Pin10=0.72V
Pin11=3.61V
Pin12=3.60
Pin13=0.76V
Pin14==0.68V
Pin15=3.66V
Pin16=0.77V
In FM mode, the discrepancies are:
Pin4=3.54V (ref. 2.6V)
Pin5=3.42V (ref. 3V)
Pin6=4.53V (ref. 4.2V)
Pin7=4.54V (ref. 4.2V)
Pin8=3.41V (ref. 3.1V)
Pin4 has the highest voltage offset, 0.9V. But...Leave a comment:
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OK, I will atempt that. I put the working unit back togrther and returned it to the house kitchen (my mom likes it there because of the radio and convenient clock). Disassemblying this radio is not difficult, but reassemblying is quite fiddling as you need to wiggle the function board to lock between all the grooves for it, all while the cables and buttons are obstructing what you are doing. ๐
OK, I will first measure the voltages on IC01 in AM mode and see if there are any offsets like in FM. If there are, but AM volume is normal in AM, the differencies of 0.X volts apparently...Leave a comment:
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Yup, I saw the procedure in the manual and it is a multistep process of measuring voltages repeatedly in different tunning. That would be very complicated for me, so I really hope nobody touched those. Their tops look untouched and in similar positions like in the working unit's old photo, so I truly hope they are OK, especially since AM volume works fine.
Is the output sound coming out through IC01? Because, after that, it looks like it passes carrying sound from FM and AM equally through other components, through the volume knob, tranzistors and out through a capacitor. What can...Last edited by UserXP; 08-14-2025, 03:37 PM.Leave a comment:
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The only manual I have is for ICF-C12L. It is the same model by look, but inside the manual, the AEP version matches my radio the most when it comes to PCB layout. My radio is model ICF-C12W.
The image attached is for ICF-C12L AEP model, it has FM and LW setting, but the board layout is exactly like the one in my radio....Last edited by UserXP; 08-14-2025, 09:50 AM.Leave a comment:
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OK, that means we can rule out bad Q1 and Q2, as well as misaligned Tx coils, then. ๐...Leave a comment:
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OK, guys, I checked Q1 and Q2 in diode mode, they appear to be NPN, positive (red) probe is on the base. They are bith 2SC930. Radio is switched off.
On Q1 (FM mix) it looks OK:
B to C =0.74V
B to E = 0.74V
Now, on Q2 (FM OSC), the readings in diode mode are:
B to C = 0.00V (but passes the continuity check)
B to E = 0.70V
Is B to C influenced by other components and is giving 0V because of that, or is it open? I really hope it is OK, because removing Q2 would be a pain in the neck.Leave a comment:
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I have no idea what you've just said, me being a layman in electronics. ๐๐ฅด But, I don't have an osciloscope, just a simple multimeter and an ESR meter. So, we'll have to try some other way. ๐ค
R_J, you are a guru in this! Yes, bridging Q7 E and C pads does turn the radio on. So now it will be a bit easier without the function board dangling and constricting movement with its cables.
Now, I also believe you are right about the trimmers. I found and older photo of the working unit main board's top wiew. The "-" grove on top of each Tx part is oriented almost exactly the...Last edited by UserXP; 08-14-2025, 03:30 AM.Leave a comment:
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