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I had my 400 II bench tested and it produced 270 watts a side at 8 ohms.

For large thermal mass PCBs you can use a PCB preheater to elevate the subassembly temperature before vacuum extracting. I find it beneficial if you add a small amount of fresh solder to the pad before extraction.

It is common practice to isolate the mains and earth (chassis) ground in a bench custom designed troubleshooting AC power supply. Many experienced electronic technicians eventually build their own troubleshooting AC power supply to get the features they want. Also common is to have a traditional factory ladder logic control scheme to operate the AC power supply control circuit, but usually operating from 12VDC which is very common for relay coil control and other control devices found in an industrial control cabinet. In a ladder logic scheme you will have a low voltage control approach controlling high voltage (120VAC) at high currents, where the two systems are electrically isolated (either magnetically or optically or both). A common feature is a series interlock where if any alarm or fault is tripped (open) the unit will shut down. These cabinets are recognizable by having a Green start push button switch (with latching relay) and a Red stop push button switch. As such it is relatively easy to include a transformer surge current limiter using a large resistor, which is then shorted out by a relay at some time after the end of the magnetization current worse case (which would include a downstream variac). I like the resistor approach because it does not use heat to operate like a thermistor, and is ready whenever the power is quickly cycled. A lot of the jitter hysteresis ON/OFF function is usually included in the 12VDC time domain relays. You can also delay when output power is available to make sure the system is stable incase there is a load on the output. It is very handy to have two analog AC ammeters in two ranges (like 10A and 2A for example) along with an output AC analog voltmeter. The analog meter movements are highly damped which can provide a clue as to the failure by watching the indicator movement upon power up. If you work on the same type of gear all of the time, like at a company repair depot, you can often know the failure just by observing the current movement behavior on power up. Setup the meter so you start with the 10A and then can switch to the 2A with a make before break switch. If you work on a lot of gear I find you only really need one current limiting device (other than several different CBs in parallel 1A, 3A, 10A) because the failure mode is almost always a direct short or almost a direct short. I am using using a 220 ohm automatically cooled low inductance 600W power resistor as my current limiting device, it is put in or out of with a shorting switch. It is very handy to have a large power toggle switch to enable power to the output isolated AC receptacles. You can buy a Hospital Grade Toroidal Isolation transformer stand alone without the case and connect it as you like. For a large transformer, features include an automatic reset thermal cutout and a separate shield. For large company repair depots, there is a troubleshooting bench and a separate outgoing test/calibration bench. The calibration bench will have a pure sinewave AC power supply where the earth ground is not isolated but the mains are, mainly for personal safety. The instrumentation test pure sinewave AC power supply can include an AC power analyzer which will give many different real time measurements which can be very specialized, like power factor, AC voltage distortion (THD), AC current distortion (THD), as well as have a large operating range for testing universal (switching or selectable) equipment. The outgoing test procedures can include calibration and testing at specific AC voltages (if it is a power supply this would include line and load regulation). It is possible that a three phase Y (with neutral) as wired for a street of homes may not string the neutral to the single phase transformer along with two phase connections. In this case the two terminal transformer primary will not include the neutral. As such the pole transformer neutral for lightning protection will be derived from the secondary neutral (includes the transformer case through a jumper connection). The Y neutral will be available along the primary main backbone feed (which includes the neutral connection to ground at each backbone pole for lightning protection), but not necessarily the street feeds having only two high voltage feeds. If you had three identical streets each would use two phases in sequence such that the load is balanced per street. It is interesting how different power companies come up with creative solutions for high voltage distribution, which at times can get very creative in how transformers are connected as derived from three phase Y or Delta.

What kinda sissy opens his video with a safety warning?

I recently completed my troubleshooting isolated variable 10A AC power supply with some features you might be interested in as compared to the unit on your bench. This is actually the third troubleshooting AC power supply I have either built from the ground up or modified from off-the-shelf. 1) I replaced current limiting bulbs (I don't like the inrush or glass or burning out) with automatically cooled power resistor 220 ohm 600W on a heatsink for equipment with a dead short, switched in and out of the circuit with a make before break switch. 2) I use floating ground duplex receptacles (one 15A and the other 20A GFCI) instead of single floating round receptacles on the output of the variac which is after the isolation transformer. Mainly for the better construction available and floating ground but also to support more insertion cycles. The high quality orange floating ground (ground not connected to mounting straps) hospital or industrial grade receptacles are very well made with large power screws and large wiping blade connection surfaces. The GFCI can be used as a crude AC leakage detector (around 6 mA max) when used as a tied neutral ground at the output of the isolation transformer. I have a switch to enable or disable the protective earth connection on the GFCI and to un-isolated ground on the 15A receptacle. I have a separate Hioki AC current leakage clamp meter I used for equipment outgoing final test, but the GFCI is a good quick test before moving over to the calibration bench (traditionally different than the troubleshooting bench). 3) I have three AC circuit breakers in parallel (1A, 3A, 10A, only one used at a time) as a equipment fuse saver. They are trip free hydraulic/magnetic Airpax marine type AC CBs (also UL1077 type would work) where you can choose the current trip profile (called delay curves by Airpax) to trip before a slow blow fuse of a similar rating. 4) For the large isolation transformer and variac (magnetic devices) I have a time delay in-rush power resistor based current limiter circuit to supply the magnetization current before enabling the output. This is needed on large isolation transformers. More stuff: I do all of my troubleshooting with isolated test gear: A Fluke DMM and Scopemeter. For calibration I use a different AC power supply (pure sinewave) and a Picoscope with high voltage differential probes to take data incase I need to include the data in a report.

Hi, big fan of your videos. Have a question on the MARANTZ 15 if you can help. Trying to figure out the diode sub for BTR1557 which I can't cross and is CR103, 105, 106, 107 can I use 1N4148 and for MR2360 which won't cross and is CR102, 108 can I use 1n4004-07?

Hi from mallorca spain .. Really enjoy your videos..especially as I own the SA8100 was a gift 35 yr ago.. I've managed to accompany it with a TX 7100 tuner CT 7271 cassette My 8100 also has this issue.. would you think the transistors you used would be compatible in my 8100...? I will be getting it looked at in a service shop.. Many thanks in advance.. Keep the great videos up..must take hrs to actually film n edit.. Regards Anthony

I had a pair of these when they came out. and I had a sub .I hung them upside down and about 6ft. high. when RadioShack went out of business I bought 4 of the tweeters for almost nothing I passed them down to my daughter and they still use them today ! as I recall the ribbon tweeters were 360 degrees

Nicely done! Congratulations, and thanks for the video!

It was old school before class d amplifiers.

Actually just happened to me last night. I bought a Sansui TA300, did the usual cleaning, deox and scope readings to check power, adjusted the bias. Was cranking along pushing the volume a bit, then poof. Nothing. Yep 32 volt car fuse across the main power. Took out an output transistor. Now in elbow deep swapping all outputs and recapping as one of the main caps was down to 60-70% of rating. It was sounding really nice, so I’m going to go through all the boards to recap.

Hi, I have an ST-4 that calibrates and tunes fine but the wheel won’t start turning unless I really close the air gap to get it moving. Then I have to I recalibrate it. Then it works fine. I think I have a weak tube or some other component. Any guess? Nothing is burnt or leaking.

Modern capacitors are so much smaller I can see where the outside foil could be less of a "thing".

Does the camcorder stop at exactly 1:00 or 2:00?

I'm guessing that this is a class-A amp, due to the massive power supply for a mere 70 watts output. A class-A amp consumes the most power when it's idling!

Why not try it at 9,10,11,12'o clock listening volume ?

A lovely amp with some cool and well thought out design - after taking off the panel, it's all so easy to work on. I love it. Point-to-point wired output transistors are a nice touch, I'm not sure about the reliability of the sockets though.

We serviced a lot of 700's as well as the 400. We always used the original Delco manufactured output transistors (PL909) as others created more troubles.

Hi Tony love your. Can you please do a demo on how to alter wiring on a vintage receiver to add a powered subwoofer. thanks

Cool! Another Rush fan!

I believe the LF oscillation you are seeing is ONLY due to the dim bulb being used. If you had genuine line voltage at 100v, or 90v or whatever, because of the low source resistance of power lines you would be fine with no oscillation, but restricted in output power. The dim bulb adds resistance in line with the power source and the voltage will then vary with the power whereas just a low voltage would be constant with varying power. Its like the bulb turns the amp into a relaxation oscillator. That also means you wont see any LF oscillations with a variac, at least not a decent one with good regulation and low source impedance. Dim bulb is only of real utility for determining catastrophic failure, it is not good for running devices at reduced voltage.

Just saw this video, Tony this is really BAD advice to be putting out there, at 22:25 your telling people to remove the safety ground. Thinking you just open yourself to be sued. It's against electrical code to do as your suggesting here, should a fire ever happen in your house for what ever reason and the investigation show it started even in the area of your work bench, the insurance company will you use this video to aid in the denial of coverage (we all know how fire investigator love to blame electrical when they can't determine reason for fire) Better solution to the problem your trying solve here is replace the non polarized cord with polarized one & wire it correctly. Your disclaimer at the beginning of the video won't save you in a law suit.

This model, and the x-28 Skyrider are at the top of my favorites, along with the Panasonic RF-8000 and the Sony CRF-320.

Can`t you just buy the cassette adapter that also has AUX in capabilities? I have one kicking around somewhere that I used in my Dodge van that had cassette. Used it for my IPOD.

My Hafler DH 500 has the fan inside, with the exit at the back surface, no impedance to flow at the cooling tunnel exit. It does not have managed speed though. It’s going to be my next project.

Oh those Oak Island boards are real treasure! 😂

Another interesting one here Tony ! I'm being very careful with my two incan dim bulbs geez where do i get a replacement these days !?!

Excuse me again, Is it possible to know who did the faceplate reproduction? Thank you

Excuse me, this is part 6. Are there anywhere parts 1;2 etc ?

I love this video on several levels. I have restored several of these, and I went through several pots of coffee pondering the LF Osc until I discovered I wasn't feeding it enough current. Looking forward to more vids! Thanks.

Dang, my 400 has +/-85 volt rails, I wish it had 48. The transformer is a 1:1. It was doing sub duty, just idling one day and then went bananas, trying to take out my sub. Luckily it was 2 15's that could take the punishment. Speaker protect circuit is a good idea. I've seen the upgrade boards but I don't know if it's worth it.

Presently own the Phase Linear 5100 Series Two Tuner and a 3000 Series Two Preamp! Had the 400 amp shown but it blew up years ago!

I have to say that this is one of the most instructive videos I've seen regarding the actual operation of an electrolytic capacitor, based on it's age and type, that I have ever seen, and your video even suggests that other circuit components may have similar issues due to their individual properties. What an eye-opening demonstration!

ca. 29:00... I think either the schematic or your explanation is wrong. Q1 isn't gonna just "turn on", but will act an emitter follower-following the signal. That makes sense...I think :-) D3 isn't switching-it's constantly conducting (I'm assuming it's a zener). It's "rail modulation".

Phase Linear started in a bay in back of and below the Tradewell store in Edmonds, WA - where I lived. When Carver built the building in Lynnwood just seven miles to the east, all of my high school friends worked there to get the discounts on the equipment. Most of my friends got their speakers from Speaker Lab in the university district by the University of Washington. Speaker Lab sold kits, and everyone was building their own. When you think about it - that much innovation in such a small area for stereo buffs was nirvana, no matter how hot the equipment got. I was known for blowing up tube guitar amps - no big deal. Just a little goofy history on very, very early Phase Linear.

Voltage is moving cuz your finger heat!!! ~2mV/K.

Blimey ! there have been a lot of awesome channels caught out by forgetting what the dim bulb does. Dim bulbs show you a dead short and protect your amp. Just because the bulb is lit doesn't automatically mean there's a problem, what wattage is your bulb ?....great vid ...cheers.

Ummmmmm.....are those diodes sposeta be in PARALLEL!?!?!?

Oh yea... What is that cute little scope you have there?

@alvinsilcott2036 0 seconds ago the original op Amp used in the phase linear amps were a LF351..wouldnt the "upgrade" to modern day op-amps with much larger bandwidths ...higher slew rates & near infinite input impedances amount to instabilities (parasitic oscillations) partially due to the absence of decoupling/bypass capacitors thru out the amplifier ??

Great videoTony. When checking DC offset should the speakers be connected or not? Seems to be some controversy about this in some of the audio forums. Thanks!

I made a tool for holding the output transistors from a wood dowel with a hollow end (snug fit to can), to facilitate keeping fingers clean while installing the transistor.

looking forward to the 700 - I have one lying around here that needs fixing.... Thanks for those great video. I wonder if these videos can be used for AI model training... just image what would do to the repair world....

"More schematic thing," Love your use of it schematic to explain the operation of the component on your bench.

"if your all good little boys and girls........" theres no girls that watch this channel !! this channel is literally 'man cave tv' :)

Excellent explanation.. Thanks for the information. It would be better if you could create a video demonstrating how the APC unit of sx-1980 works.

Hi Tony. The “back-and-forth” Cylon Eye/K.I.T.T. “display” are called, “Larson Scanners” after Glen Larson, the producer of Battlestar Galactica and Knight Rider. At least that’s what I heard. Whether it’s true or not, I don’t know. 😊

Back in 1979 I purchased my first stereo at our local hi-fi shop which was a Pioneer SA-6500 II integrated amplifier, Pioneer HPM-30 speakers and a Panasonic SL-H401 direct driver turntable (I still have the turntable - I wanted a Technics but it was outside my budget). Two things I remember so well: 1) the smell of the owner's pipe tobacco and 2) in the back of the store with the "high end" gear the Phase Linear power and pre-amps including the 400 and 700. Those were WAY outside my budget.

Is this an Italian unit?

Add some PS bypass filtering, esp around those op-amps. It can't hurt and only can help