Hey Jaycee/Mooly.
Jaycee - yep didn't think about that - the amp looks pretty modern style-wise and have to keep reminding myself it's an amp from the late 70s haha! It's not as bad as I thought though now I've had it playing a few times - first time switching on I think all the senses were 'on edge' incase anything happened
My DAC is less than 2V output so I think it'll all be OK in the main system volume-wise.
Mooly - It's sounding very good considering there's caps in the signal path which haven't been changed since approx. 1978-1980! I'll get to those at some point but just want the PSU and the 'essentials' to be fixed for the time being so it works safely - blown my budget as it is
Since last testing I've installed fresh caps on that PSU board (C801/805 & C802/803). Is it OK to listen with those in circuit still as C801/805 (which usually connected TO the smps) are not connected at the moment. Will this harm them?
Resistors arrived for the SMPS today and they've all been soldered in. All I need is the MJE350 to arrive which replaces A911 for Q603 and I can start testing that. Perhaps by the weekend it'll all be back together again and singing sweetly!
- J
Jaycee - yep didn't think about that - the amp looks pretty modern style-wise and have to keep reminding myself it's an amp from the late 70s haha! It's not as bad as I thought though now I've had it playing a few times - first time switching on I think all the senses were 'on edge' incase anything happened
My DAC is less than 2V output so I think it'll all be OK in the main system volume-wise.Mooly - It's sounding very good considering there's caps in the signal path which haven't been changed since approx. 1978-1980! I'll get to those at some point but just want the PSU and the 'essentials' to be fixed for the time being so it works safely - blown my budget as it is
Since last testing I've installed fresh caps on that PSU board (C801/805 & C802/803). Is it OK to listen with those in circuit still as C801/805 (which usually connected TO the smps) are not connected at the moment. Will this harm them?
Resistors arrived for the SMPS today and they've all been soldered in. All I need is the MJE350 to arrive which replaces A911 for Q603 and I can start testing that. Perhaps by the weekend it'll all be back together again and singing sweetly!
- J
Wow, I never thought of this before, so I started looking around and found this:
150mV/100k? Does that mean my impedance would have to be 1.34Mohm for a 2V input? i'll have to check this data against the manual I have when I get home.
John--glad to read about your progress!! Don't get too excited
None of the caps will come to harm, C801 and C805 shouldn't even be powered up at the moment with using another PSU. C802/3... no problem there.
I was just looking at the circuit generally. The VU meter. Give the "calibration" pot a whizz to and fro (little WD40 on it maybe) as that may be the problem. We can calibrate them properly anytime. Old preset pots do go dicky.
Ws looking at the opamp in the tone controls... that looks a favourite to upgrade. Not looked up the HA fitted so not sure if it's a DIL or SIL package.
I was just looking at the circuit generally. The VU meter. Give the "calibration" pot a whizz to and fro (little WD40 on it maybe) as that may be the problem. We can calibrate them properly anytime. Old preset pots do go dicky.
Ws looking at the opamp in the tone controls... that looks a favourite to upgrade. Not looked up the HA fitted so not sure if it's a DIL or SIL package.
Wow, I never thought of this before, so I started looking around and found this:
150mV/100k? Does that mean my impedance would have to be 1.34Mohm for a 2V input? i'll have to check this data against the manual I have when I get home.
John--glad to read about your progress!! Don't get too excited
The input impedance is (to all purposes) constant on a given input. Those sensitivities are a carry over from the DIN standard, which I guess something of this age could easily have been used with.
Neither of the meters are moving that much, so I think as you say those pots need working, plus the relevant caps need replacing too. I doubt (touch wood!) there's anything too serious wrong with them as they appear to be sealed units. At any rate they're pretty low-down on my list of things to do to the amp.
Next stage the SMPS.
Listening to it at the moment and it's extremely clear sounding, and sounds pretty well balanced from top to bottom so far. Surprising kick too!
Going to spend the rest of the evening ploughing through some favorite albums!
Thanks again guys!
- John
Next stage the SMPS.
Listening to it at the moment and it's extremely clear sounding, and sounds pretty well balanced from top to bottom so far. Surprising kick too!
Going to spend the rest of the evening ploughing through some favorite albums!
An externally hosted image should be here but it was not working when we last tested it.
Thanks again guys!
- John
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That's good
Just quickly looking at the circuit the meters are simple passive "wattmeters". In other words they measure voltage at the amp output and by assuming a load of 8 ohms are calibrated to give the power that that voltage equates too.
They are "insensitive" as such at low levels, partly because the diode volt drop in the meter circuit has to be overcome. Germanium diodes are much better for this type of application (not sure if the 1S1555 is SI or GE without checking)
Just quickly looking at the circuit the meters are simple passive "wattmeters". In other words they measure voltage at the amp output and by assuming a load of 8 ohms are calibrated to give the power that that voltage equates too.
They are "insensitive" as such at low levels, partly because the diode volt drop in the meter circuit has to be overcome. Germanium diodes are much better for this type of application (not sure if the 1S1555 is SI or GE without checking)
That's good
Just quickly looking at the circuit the meters are simple passive "wattmeters". In other words they measure voltage at the amp output and by assuming a load of 8 ohms are calibrated to give the power that that voltage equates too.
They are "insensitive" as such at low levels, partly because the diode volt drop in the meter circuit has to be overcome. Germanium diodes are much better for this type of application (not sure if the 1S1555 is SI or GE without checking)
Yes insensitive is definitely how I'd describe them at the moment haha! The left one is sort of stuck around 0.01 (you can just about see this on the pic above), the right is moving about half an inch depending on the signal.
Still no matter - the music really does sound great! I can see how this was considered a high-end amp in its day. Looking forward to getting that SMPS installed tomorrow or Saturday.
And don't worry folks I promise I'll take it slow
...what to play next..... hmmm......
- J
They really are - the aluminium fascia is approx. 5mm thick on this and beautifully finished. All the controls levels etc are all solid and work well. And that ALPS volume control is something else - 4-gang large unit, and enclosed in a die-cast covering rather than the usual plastic.
More about it here: Sony TA-F6B on TVK
http://www.proteus.pl/~gpietkie/Vintage/Sony_TA_F6B/index.html
Right I'm off to really get some serious listening done folks. Once again thanks for all the help. And Mooly - you is da man, as the yoof say these days!!!
Cheers,
- J
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We'll worry about the meters again. The bearings in the meter might be sticky, they are very much like watch balance wheel. The meters do come apart as a last resort, the front unclips usually but that really is a last resort. There is a mechanical "zero" adjustment too.
With the amp off if you put your meter on diode range across the meter terminals the meter should flick fully over one way, reverse the leads and it goes the other way. That might free it off if it's sticky.
That's it for today... enjoy
With the amp off if you put your meter on diode range across the meter terminals the meter should flick fully over one way, reverse the leads and it goes the other way. That might free it off if it's sticky.
That's it for today... enjoy
Hiya!
That MJE350 didn't arrive today which is a pain as it's the only component I need to finish the SMPS.
As you'll recall I ran basic diode conductivity & short checks on the existing A911 (Q603) and it tested OK. Are there any other tests I could easily run to see if its OK? I'd rather use this original part rather than waste it if possible.
- John
That MJE350 didn't arrive today which is a pain as it's the only component I need to finish the SMPS.
As you'll recall I ran basic diode conductivity & short checks on the existing A911 (Q603) and it tested OK. Are there any other tests I could easily run to see if its OK? I'd rather use this original part rather than waste it if possible.
- John
Hi John,
Is that part all that's stopping you firing it up... the basic tests are all you can reasonably do, although reading on the highest ohms range (the one you use to measure say a 1 meg resistor) from C to E would be worthwhile. Black lead to C and Red to E and it should not read.
If we test the psu slowly then if that part is faulty it will show.
Is that part all that's stopping you firing it up... the basic tests are all you can reasonably do, although reading on the highest ohms range (the one you use to measure say a 1 meg resistor) from C to E would be worthwhile. Black lead to C and Red to E and it should not read.
If we test the psu slowly then if that part is faulty it will show.
No good... not high enough voltage.
If the original seems OK we can risk fitting and powering up just the PSU with a bulb. Do not connect the PSU to the amp of course, and leave the four switching transistors out for now.
Initially it's a case of switch on and observe for a few seconds. Make sure the bulb goes out, if it doesn't power off immediately.
If it's OK we do some voltage tests.
If the original seems OK we can risk fitting and powering up just the PSU with a bulb. Do not connect the PSU to the amp of course, and leave the four switching transistors out for now.
Initially it's a case of switch on and observe for a few seconds. Make sure the bulb goes out, if it doesn't power off immediately.
If it's OK we do some voltage tests.
So you mean connect mains directly to the input side of the SMPS (leaving the amp out of the picture completely, for now), using bulb for fuse. Been reading that the SMPS carries 400V DC so it might be time for.... The Rubber Gloves (cue thunderclap!!!).
Powering up without the four switching transistors won't cause any harm to the SMPS then?
EDIT: looking at the circuit diagram again I realise I need to connect DC to the SMPS (not directly from the mains as I stupidly asked above!). Take it I connect the leads from PSU board C801/C805 to the input of the SMPS? As well as put a jumper wire for the 0V from SMPS to the chassis?
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What would a daily thread by like without any pics!?
Here's the SMPS with all-new caps plus several new Kiwame resistors:
...and here's the SMPS connected to the amp. To the output end of the SMPS I have soldered a couple wires connected to a nylon screw-block. Makes it easier to test the output voltage then by touching the multimeter probes to the screws in the nylon block. Keeps me further away from those dangerous high voltages.... I know - Mr Wuss-pants!
Here's the SMPS with all-new caps plus several new Kiwame resistors:
An externally hosted image should be here but it was not working when we last tested it.
...and here's the SMPS connected to the amp. To the output end of the SMPS I have soldered a couple wires connected to a nylon screw-block. Makes it easier to test the output voltage then by touching the multimeter probes to the screws in the nylon block. Keeps me further away from those dangerous high voltages.... I know - Mr Wuss-pants!
An externally hosted image should be here but it was not working when we last tested it.
