Hello guys, I´m restoring a vintage Pioneer integrated amplifier. Originally this Amp comes with a 2x18 awg power cable, meaning that it only carries 120 volts and neutral.
I want to upgrade it with a 3x12 awg in order to carry 120 volts + neutral + ground.
My question is: since the power transformer, circuit and components where not originally designed to be grounded, will I have any problems if I ground the amp's chassis?
Is it beacause that at the time the amp was made (1,978) was not common to have grounded outlets at home at that it why it was not taken in care?
Or beacause it is not recommendable since it was not considered to be grounded at the power outlet?
Will I improve anything or will I damage something? Any suggestions are welcome.
Thanks in advance.
SkyWay
I want to upgrade it with a 3x12 awg in order to carry 120 volts + neutral + ground.
My question is: since the power transformer, circuit and components where not originally designed to be grounded, will I have any problems if I ground the amp's chassis?
Is it beacause that at the time the amp was made (1,978) was not common to have grounded outlets at home at that it why it was not taken in care?
Or beacause it is not recommendable since it was not considered to be grounded at the power outlet?
Will I improve anything or will I damage something? Any suggestions are welcome.
Thanks in advance.
SkyWay
It was designed by a good manufacturer without a safety ground, so you dont need one. You might cause problems( ground loops) if you add one. Leave it alone.
My SA-606 came grounded via factory IEC plug. Ground (PE wire) is connected to chassis. Circuit ground is connected to chassis via Phono ground. Since this bolt was bad, I've soldered a thick 2.5mm wire from the middle of the 8000uF capacitors to the chassis.
If You download the schematics, usually they include the different PSU schematics connections.
Cassette deck, Tuner & Turntable also feature a factory IEC plug.
In 1978 here in Portugal ground PE wire was mandatory in kitchen, laundry, heating appliances & industrial machines which had to have it's own circuit with breaker.
My system was acquired in Germany and there were Schuko harnesses used for long time. I believe they were mandatory, since every house were I lived had them including in the bedrooms.
If You download the schematics, usually they include the different PSU schematics connections.
Cassette deck, Tuner & Turntable also feature a factory IEC plug.
In 1978 here in Portugal ground PE wire was mandatory in kitchen, laundry, heating appliances & industrial machines which had to have it's own circuit with breaker.
My system was acquired in Germany and there were Schuko harnesses used for long time. I believe they were mandatory, since every house were I lived had them including in the bedrooms.
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Quite potentially yes.
Going IEC Class I is generally bad news when using unbalanced audio connections, as hi-fi traditionally does.
In any system like that, you want one and exactly one ground connection. If that's already on the amplifier, you will run into trouble when connecting your PC.
The mains leads on devices as old as this may still be single-insulated (if you can clearly see two separate conductors from the outside). That's definitely not up to modern safety standards. All the mains wiring outside and inside the device should be carried out with modern double-insulated cable, and if you need any solder connections they should be heatshrinked and all. The keyword for IEC Class II devices is "double insulated". No single isolation fault may be causing the device to go live.
There is still use for a 3-conductor mains cable with polarized plug. My thoughts on the matter:
1. 12AWG may be a bit of pig to handle. What's that typically used for, heaters and other high-power equipment? I would look to see whether they have anything similar in more like 16AWG (even the original 18AWG would be just fine really, just don't buy any copper-coated Al crap). C'mon, it's just a little old integrated amp with a mere 3 A fuse rating, no need to go overboard here. The absolute minimum would be a mere 22AWG.
2. Set the amplifier by itself onto an insulating table and conduct a test of hum on an open input in both positions of the original mains plug, maybe with a short length of audio cable laying about. Verify and note down the position with less hum, and trace out where that puts your L and N. Then wire the new cable with polarized plug to match that. Take care to ensure that the mains power switch ends switching the live.
3. The third, protective earth conductor is not for nought, though I would not wire it to chassis right away. Instead, get a Y2 class (safety) film capacitor of maybe 4.7 or 6.8 nF to connect the chassis and PE. This is (a) small enough to not cause any dramatic ground loop issues yet (b) still substantially larger than internal transformer capacitance, hence keeping the device near ground potential at all times and minimizing open input hum.
4. Get 2-conductor double-insulated mains cable for internal wiring, unless what's already there is already up to the same standard.
You do realize this potentially makes a difference in terms of RF ingress? At the phono jacks seems the most sensible place to put a chassis ground connection.
Outlets have been Schuko here for a long time. They were similar round ones with no PE contacts before that.
Plugs could be anything from Schuko, contour (CEE 7/17) up to Europlug. HiFi stuff is usually Euro since at least 1980. Maybe Pioneer's construction wasn't entirely up to double-insulated standards, or they were just overly cautious? I can't say what Kenwood did in my '79 KT-80 was particularly confidence-inspiring.
If you see any potential for ground loops in your system, I would look into reviewing the mains-side wiring and bringing it up to a modern-day IEC Class II standard.
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I agree with cbdb - ground loops could be resulting from modifying the growning scheme.
Pioneer vintage equipment never needed a 3rd ground wire.
Pioneer vintage equipment never needed a 3rd ground wire.
Done.
Last year I rebuilt a tube amp and replaced the old cord with a nice quality 2 conductor
cord and used a belt sander to make both prongs the same size like the original
That could be plugged in either way (can be flipped) to minimise hum if needed.
I have another amp that was a Kit from Japan and it came with a 3 conductor cord
That has a two prong plug with a ground wire so it can be flipped.
When I first hooked it up I used a cord with a 3 prong plug and had a hum issue,
So I put on the stock cord without connecting the ground wire and the hum went away.
cord and used a belt sander to make both prongs the same size like the original
That could be plugged in either way (can be flipped) to minimise hum if needed.
I have another amp that was a Kit from Japan and it came with a 3 conductor cord
That has a two prong plug with a ground wire so it can be flipped.
When I first hooked it up I used a cord with a 3 prong plug and had a hum issue,
So I put on the stock cord without connecting the ground wire and the hum went away.
Here's luck for ya - I was testing an old Heathkit AR-1302 receiver on the bench and needed a quick audio input. I had an iPhone 4 playing in the dock of a Sony S-master receiver, so I figured I'd simply connect the headphone output of the iPhone to the aux input of the heathkit...while still in the Sony receiver's dock.
The iP4 screen immediately went all horizontal lines and then black when I plugged into the headphone out. Gone / Dead. Curious, I measured between the ground of the 3.5mm plug and the shell of the Sony dock - 10.5V. Reversing the AC cord on the Heath (plugged into my variac), still 10.5V. I have no idea how that could possibly be.
Final result is whatever powers that be were successful in eliminating my easy-peasy wireless internet streaming music in the garage.
I spose it could have been worse. Anyone want to buy a set of Heathkit quasi-comp amp modules? Tested and play music (from the working AM section of the receiver)...
The iP4 screen immediately went all horizontal lines and then black when I plugged into the headphone out. Gone / Dead. Curious, I measured between the ground of the 3.5mm plug and the shell of the Sony dock - 10.5V. Reversing the AC cord on the Heath (plugged into my variac), still 10.5V. I have no idea how that could possibly be.
Final result is whatever powers that be were successful in eliminating my easy-peasy wireless internet streaming music in the garage.
I spose it could have been worse. Anyone want to buy a set of Heathkit quasi-comp amp modules? Tested and play music (from the working AM section of the receiver)...
Inside Pioneer SA-606 Amplifier | Piano Piano! | Flickr
Can You see the green PE wire connected to the chassis ? I believe it's used on European models 220/240V type HG.
.
No, actually there is less hum with volume cranked up with no record playing.
This happened to my Samsung phone when connected to a friends mixing desk jack input.
Turned out it was a +25V supply PCB track under the jack & the jack tip was making contact when fully inserted. Bad design !!
Connect a ground PE wire to the chassis before drilling & test.
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Thank you very much guys for taking the time to read and respond.
I ended up following advice and left it the way it was with the original power cord.
What I did was changed the blown thyristor model BCR 3AM-4 (3A,200V) with the replacement i found model 2N 6071AG (4A,200V) and the 2 resistors connected to it that where open (0.5 Ohms 2 watts).
Also I recapped everything respecting the original design and replacing electrolytics with Nichicon Electrolytics and ceramics with polypropylene and small values with c0g/np0 capacitors.
High wattage resistors (0.5, 1 and 2 watts) where replaced with Vishay Dale metal film resistors.
Today I tested the amp, and when I turned it on, the heatsink became hot in about a minute without any input or speaker wire connected, I turned it off and let it cool down for 30 minutes, then I plugged input signal and speakers and turned it on again and played some music, but it sounded distorded and in less than 2 minutes the heatsink was hot again and the main fuse (3A) blew up.
Can you guys help me out and advise me with possible solutions to the problem?
Again, thanks for taking the time to read.
SkyWay
I ended up following advice and left it the way it was with the original power cord.
What I did was changed the blown thyristor model BCR 3AM-4 (3A,200V) with the replacement i found model 2N 6071AG (4A,200V) and the 2 resistors connected to it that where open (0.5 Ohms 2 watts).
Also I recapped everything respecting the original design and replacing electrolytics with Nichicon Electrolytics and ceramics with polypropylene and small values with c0g/np0 capacitors.
High wattage resistors (0.5, 1 and 2 watts) where replaced with Vishay Dale metal film resistors.
Today I tested the amp, and when I turned it on, the heatsink became hot in about a minute without any input or speaker wire connected, I turned it off and let it cool down for 30 minutes, then I plugged input signal and speakers and turned it on again and played some music, but it sounded distorded and in less than 2 minutes the heatsink was hot again and the main fuse (3A) blew up.
Can you guys help me out and advise me with possible solutions to the problem?
Again, thanks for taking the time to read.
SkyWay
All I've seen on this thread is that it's a "something" Pioneer product from the late 1970's.
No model number.
That's like asking over the phone to a doctor - what's wrong with my health?
No model number.
That's like asking over the phone to a doctor - what's wrong with my health?
Sorry, it is because part of this thread is from a previous one.
Pioneer SA-606 integrated amplifier from 1,978
Pioneer SA-606 integrated amplifier from 1,978
Wire a 100W incandescent lamp in series with the amp & start troubleshooting in order not to blow more parts. Probably with the new caps it is oscillating. You should have tested it before recapping. The protection circuit kicked in because of some reason.
Replace only the elkos. Leave the ceramics alone. There are also a few orange bipolar inside. Check
Check the triple diode legs under the heatsinks ST3VH. They are unobtanium. If broken amp tries to short the output drivers.
Check also if the transistor legs are seated in the connectors.
When I repaired mine, one channel was distorting because one of the channels transistor was out of the socket.
Replace only the elkos. Leave the ceramics alone. There are also a few orange bipolar inside. Check
Check the triple diode legs under the heatsinks ST3VH. They are unobtanium. If broken amp tries to short the output drivers.
Check also if the transistor legs are seated in the connectors.
When I repaired mine, one channel was distorting because one of the channels transistor was out of the socket.
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Thank you very much for taking the time to reply, I think the problem comes from one of those Varistors you mentioned the STV3H.
Will wire the incandescent bulb and proceed to check part by part.
Thanks again, I will inform based on the results.
Have a great day.
SkyWay
Will wire the incandescent bulb and proceed to check part by part.
Thanks again, I will inform based on the results.
Have a great day.
SkyWay