Відео

It is definitely possible, the headphone jack is run off of the op amp before the power chip. It could also be because of the 10uf capacitor that feeds the signal to pins 4,5 of the power chip.

@@leonardpeters3266 Thank you so much for the reply and info. I've ordered the new chip and will let you know what happens once I've installed it! If that doesn't fix it, I'll check out the 10uF cap next.

Yes those 6X5s are indeed transformer eaters.

The place I bought them no longer has them. I would look at the parts for a Shop Fox Parts for W1877 - 13" Benchtop Planer. Look on Grizzly tools. I believe they are the same. www.grizzly.com/products/w1877/parts

I'm glad it helped. I think as long as you have the amp opened up, why not put it in. That way, spend $1.50 and you won't ever have to open it up again.

@@leonardpeters3266 Oh, I should have asked; What type of cap did you use for the roach to ground cap? And where do you get your capacitors and components?

@@ranger44881 I used a Sprague orange drop capacitor. It is what I had on hand. I also used sprague electrolytic capacitors for the cathode bypass caps. I used F&T capacitors in the dog house. I got my tubes from Antique Radio Supply (tubesandmore.com). I also got the capacitors there. They do sell kits of caps for Fender amps (Mixed Sprague Atom and FT) www.tubesandmore.com/products/cap-set-fender-twin-reverb-ab763-black-face. But I couldn't find the Sprague orange drops. Any good bi-polar capacitor will work. I have had very good results with Illinois Capacitor Polypropylene. www.tubesandmore.com/products/capacitor-630v-polypropylene-axial-leads

Right back atcha Liz. Things are going along fine. Hope you're doing well too.

What model is that?

Its the MM65 Twin, I got it around 78 or 79

@@fubopnation8624 So I am assuming it is either a 2475-65 or a 2275-65. I would start by replacing the power supply capacitors (C42,C43,C44,and C45). You might also want to check the 6CA7/EL34 output tubes to make sure they're up to snuff. There is another set of capacitors in the power supply section that supply low voltage (C46 and C47 possibly C31 and C32 as well). It would be good to make sure they are in good shape. Outside of those suggestions I would have to have it in front of me. The Celestion speakers would be a nice touch.

That is a great question. I actually use the a ground lead from the EICO. It gives me allot more flexibility for placement and also frees up movement with the probe. It also quiets the probe down when working in a chassis. I liked the setup so much I used it on my Ultraprobe as well.

@@leonardpeters3266 - Ahh, ok. I’m in the early stages of building a stand alone Carlson Super Probe. I might copy you and just put a 4mm socket/binding post on my amp/speaker unit for a grounding lead. It seems to me that it would be neater for occasions where you can’t use the grounding lead and would otherwise be holding it in your hand as well as the probe.

@@alexwade9921 If you can skip to the Ultra Probe it would be well worth it. I have had incredible success with it. Here is a video demonstration of it ua-cam.com/video/RIlTA8PcbpI/v-deo.html

@@leonardpeters3266 - I haven’t heard of the Ultra Probe. Is that another Carlson design? Are there PCB’s etc available for it?

@@alexwade9921 Yes it is available on his patreon.

Thank you for the kind comment

SMPS

The Eico was16 dollars at an estate sale, and it came with an isolation transformer. I did build that probe with through hole components on a perf board, that's why it is in a 3/4 inch copper pipe. But I got a 70 dollar microscope with lcd display for Christmas. I built the Ultra probe and amp with SMD components and once I got used to it, it wasn't that bad.

@@leonardpeters3266 $16 with an isolation transformer? WOW! What a find! I have a LCD microscope I bought for fixing hair wire coils. I guess I could pull it off with that. I'll have to give it a try. Anyway, loved the video Leonard! Thanks! Paul

@@ElectroRestore Good tweezers are also very helpful.

Thank you for the kind comment.

Thanks I will try to put a couple out this summer.

That's great.

The STA540 is actually 2x 34 W into 8 Ω at 22 V, 1 kHz, 10% THD. Or 2x 15 W into 8 Ω at 16 V, 1 kHz, 10% THD. It is my belief that they chose to run it in between with a large heatsink to maximize the life of the chip and minimize failures. Several parameters would need to be analyzed if modification were intended, not the least of which would be power supply capability. I think I would stick with the original design.

I identified the bad MOSFET by comparing diode tests on both channels. This is not intuitive because diode testing on a Fluke is typically not used on FETS. But I was able to find differences in the readings between the 2 channels on the bad FET vs. the good one. It is unfortunate that the manufacturers do not provide schematics, it would really help. In your case I would want to chase down the balance issue and find out what was causing the difference. you might have a bad coupling capacitor that is causing both problems. Of course it is impossible to say for sure. One of the things I did notice is that the Anthem appears to be a straight discrete transistor amp, this would make checking it with a good VOM with a diode checker easier than a MOSFET amp. I would also check for DC voltage at the speaker outputs, maybe the bias is off a hair.

@@leonardpeters3266 Thank you again for sharing your knowledge. I'm not a professional in the electronic field. However, I have some technical skills and a strong desire to learn. At this moment, I don't have the proper tools for generating sine waves at a certain input voltage, nor an oscilloscope to read the output signal on the speaker output connectors of the power amplifier. At this moment I only have a very modest multimeter. I will use it to investigate within these limits. Is it possible to measure capacitors that are already connected in a circuit and diagnose them as being in normal parameters? And yes, there is a variable resistor on each channel that modifies the bias. I didn't play with them...

@@florinbizu5018 Capacitors have allot of failure modes and most are not measurable in the circuit. The voltmeter can be used to look at the speaker output terminals. Set the voltmeter to DC voltage and look at each speaker outputs while the amplifier is idling (No music playing). The DC voltage should be less then 20mv. Preferably less then 10mv. If it is then your bias is probably fine. I must caution you about about turning the bias variable resistors without having the alignment instructions it can cause serious failures.

@@leonardpeters3266 Good morning! I finally had time to make the measurements according to your instructions. I have set the multimeter on 200m, DC V. One mention: I have inserted one end of the black probe to the multimeter port marked 'COM', and the red probe to V - Ohm - mA port. When I connected the red probe to the plus-marked speaker terminal and the black probe to the minus speaker terminal of the 5 channel power amp, the multimeter indicated mV values with a minus sign in front of the numbers. When I reversed the probe (red probe to black speaker terminal and black probe to red terminal) the reading values on the multimeter display were positive. The results are as follows: on the front right channel (the one with the 'pop' sound at the start) I have 3.6 mV in idle. I have measured also the current at the speaker outputs when powering up the power amplifier and the multimeter showed a short brief jump and indicate -29 mV, then the 3.5...3.6 mV in idle (fluctuating between 1.6 mV, to 4.2 mV in idle). Also, after powering down the amp, I noticed a residual current of 21 mV (positive value) that dropped in 38 seconds to 5.2 mV and stayed at around this value for about a minute or two, and a residual value of 1.0 mV even after a few hours. After powering down, on the other channels I measured a residual insignificant current of 0.00...0,01 mV (probably in the error margin of the cheap multimeter). Also, in comparison, the idle current on the other 4 channels where shown as follows: for the right surround power amplifier channel module, 6.1 mV; center channel module 7.5 mV; left surround channel 4.4 mV; front left channel 6.5 mV. I didn't played/turned the bias trimmer potentiometers - they are unmoved/untouched as I found them after removing the metal cover of the amplifier.

@@florinbizu5018 This is good news. It appears that the push-pull power amps are all biased correctly. The bias is good. The residual voltage you see after power down is not uncommon, the filter capacitors are staying charged. Unfortunately I don't have a schematic of that amp and don't know if they put a discharge network in the amp. I do have a question for you though. I imagine each of the channels has a protection relay. Can you hear the protection relays engage on startup? Also do they engage at the same time?

Great, I wish you well and hope you enjoy the radio.

@@leonardpeters3266 I started today....no initial response from it. Tubes test okay. I'll start on the caps tomorrow. The switch has 3 selections, am, sw & ????

@@eugenetheodore2956 It is (counter clockwise to clockwise) {pos1 broadcast (540kc-1600kc)min.} {pos2 broadcast(540kc-1600kc) max.} {pos3 shortwave (9-12mc)}

@@leonardpeters3266 Thank you.

I quit my job expressly so I could play around.

@@leonardpeters3266 he's done his time. Play on Lenny

Thank you for the kind comment.

Boy do I remember those TV's. They were really nasty, particularly the horizontal output tubes. If you ran across the plate of one of those it would cut you open and cauterize you at the same time.

Thank you sir.

I believe it runs on 15 volts 2 amps. I still suggest not getting in the habit of putting your fingers inside powered electronics. But these are more benign then most.

did you have to have to take the voltage out of the caps? @@leonardpeters3266

I'm sure your wife will be overjoyed. Ha

Muito obrigado pelo comentário gentil. Desejo-lhe muito sucesso na sua reparação e reconstrução.

Thanks Philip, I hope your repair goes very well.

Thank you for the kind comment.

I am glad your radios perform well for you. I would refer you to an interesting video for even better performance. It is here: ua-cam.com/video/BnR_DLd1PDI/v-deo.html

Thanks for the kind comment.

It was repaired for a friend.

Thank you for the kind comment.

Thank you for the kind comment.

Yes I plan on building it this winter. Actually getting ready to order the parts right now. I intend on using the same input jack for that probe.