I just finished up building a Super Probe kit I bought on Ebay and did the mods on an Eico 147 I had reconditioned with new caps and resistors. I checked the voltages on the tube following the volume control and found that the Eico 147 vs the 147A does not have that problem of tube saturation or the voltages dropping so adding the resistor and capacitor was not needed. They stayed rock solid. Now if you compare the schematics for the 147 and 147A, you see that the 147 uses 5 tubes vs the 147A 4 tubes plus that volume control goes to a pentode tube vs a triode tube. I am wondering if that difference of tube types is the reason for better stability? I'm guess Eico decided to cut some costs by redesigning the 147. Anyway thank you for the video showing us how to mod things.
I beleieve Ridgid designed this machine to wear our at a specifice time and discontinued making parts for it so they could get you to buy a new machine. I have Several Ridgid Machine and will buy from a different manufacturer in the futur. All done here wih ALL ridgid tools because of what appears to me as designed absolence of produck. Where has the old Craftsman Brand gone.?
Hi leonard, I happen toown a Music Man twin from the same time period. Just getting ready to use again. So I started her up let her warm up, and man she sounds great. So If i wanted to get my MM twin updated, where would I start, i'm in NY?
@@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 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RIlTA8PcbpI.html
Nice conversion of the EICO 147A. I don't have a Carson super probe yet and have not needed one. Nor do I have capabilities to make small PC boards. I do like the EICO signal tracer as a test tool. It also makes a good bench amplifier for testing audio device. Good informative video! btw, new subscriber!
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
Hi Leonard I am just trying to repair an HP 8640B that has suffered front damage and I need to source the perspex front panel and a couple of of buttons. Do you have one you are willing to sell parts from Regards Colin
Thanks sir, an easy repair! The Ridgid rollers are discontinued, as far as I can tell. I ordered the following part numbers from Cutech. RP 40200-098_Outfeed Roller and RP 40200-104_Infeed Roller. $11.99 each plus shipping. For $33.97 I have a repaired machine. Thanks for taking the time to create the video!
Man, that was painful watching it be put back together I tell you a mod that would be happening pronto each pot desoldered and wires run from board to pots much easier to reinstall back into the enclosure
Hi. I have found chip that I also need to replace but have one question. It must be 20W chip or it can be 30 or 33 W? Higher audio power might occur some other problems? Or this electrical system can handle this power? Or maybe original chip have more wattage than whole amp? Cheers.
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.
Thank you also for posting this video. I have an Anthem Statement P5 with the same problem, on the right channel. A popping sound is coming out from the loudspeaker when I'm starting the amplifier, but with some particularities: - a) I'm not getting the popping sound when powering up, if I leave the amplifier unused for more than a few hours; - b) I'm not getting any audible secondary popping sound when I'm powering off the amplifier (compared with the situation that you showed in this video with the BAT power amplifier); - c) I'm noticing a difference in sound level comparing the left channel with the right channel. The right channel (the one with the popping sound when starting up) sounds louder than the left channel. To balance the volume between these two, I have to attenuate with -4.5 dB the right channel (using the Oppo 205 player settings, connected directly to the P5 amplifier). I live in Bucharest, Romania (E.U. member country) - the power grid for domestic use here, is at 230 V, 50 Hz.
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?
@@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 & ????
Carlston design would be safer for a beginner as the probe and amp are all battery powered! My early employment back in the 60’s was valve power amplifiers full of hazards! As well as 240 volts Ac you had valve anodes 500+ volts Dc etc ! I had a few belters myself which taught me to put my left hand in my pocket when probing with my right hand! Health and safety didn’t have much clout then ! Now I use an isolation transformer and variac on any mains gear I work on now! Early colour tv’s were a death trap with 25kv on the crt anodes! I always grounded any crt as they can retain high charges for weeks! Hv capacitors you have to discharge before you touch anything! I worked about 50 years on electric/ electronic equipment and I am retired now on my 79 th year! 😊
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.
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.
saudações brasileira ao mestre............primeiro parabens por seu trabalho realmente muito bom e sua didatica é perfeita...........aqui no Brasil foi lançado a decada de 1950 uma versão com ondas curtas ...........se voce acha apertado esse radio precisa ver o que estou tentando dar vida em minha bancada...........bem agradeço sua dicas e conselhos e a partir de agora vou acompalha-lo em todos seus videos, passados e futuros...........abraços a mestre e sigo por suas novas dicas
Nice coverage on this repair and very well explained. I found this especially interesting because just tonight I was at my bench setting the bias for a Fender AB763 circuit vibrato channel with reverb but no tremelo. I have 6L6WGB's however, and just a little scared about the 455vdc on the plates but, they are NOS Phiilips and have a reputation for handling that voltage quite well. Thats a pretty nifty capacitor tester you have there, would be a nice thing to have in the shop. Thanks for the well done video! NIce work.
It doesn't matter which way those yellow capacitors go in the radio. I put them in which ever way and all my radios play great with perfect sound and reception.
I am glad your radios perform well for you. I would refer you to an interesting video for even better performance. It is here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BnR_DLd1PDI.html
Lots of nice tricks of the trade. I have been repairing old amps as a hobby since 2015 or so, always more to learn. Thanks for sharing. That amp sounds great!!!
Years ago, the shop I worked at, threw out a bunch of gear that was considered obsolete, among the stuff was an HP 410B and a HP 430C, and a bunch of other stuff. Needless to say, I picked it out of the trash, and took it home. I pull it out and use it when needed, especially to double check the output of some generators to make sure the attenuators are still good and calibrated. Just because somethings are old and need special care, doesn't mean they are obsolete and need to be tossed in the trash...
Hello, informative video. I have two of the super probe boards etched, but never populated them, I wanted to knock out a couple of his cap testers (the one that shows outside foil and the one that shows micro amounts of leakage). Well now the ultra prone has been announced so I etched that board, populated it, have it in a case and all that’s left is wiring it up. Think you’ll plan on building the ultra probe? I’m doing the same thing, but with a Heathkit T-3 tracer which looks to be pretty much identical to your Eico.
Nice meter and nice video. I picked one up at a local ham/radio gathering for $10. It was in excellent cosmetic condition and came with a manual. I had to clean the switches, replace 5 resistors, the filter cap and then replaced the 6X4. The OB2 tested new and the 2 12AU7s are a pair of RCAs that tested as new and very well matched on my Hickok. I was surprised he was selling it so cheap, it looked like he had just replaced the DC and resistance leads with Probe Master leads, so I figured it would have been a mess electronically. But it calibrated right up and was dead on with the meter. Excellent device!
@@leonardpeters3266 yeah, it’s crazy what people are paying for them. Though it’s considered one of the best VTVMs ever made and top quality HP devices are commanding top dollar. A friend’s grandfather is pretty much done with electronics so he gave me a bunch of tubes and tube gear and in one of the boxes was an RCA WV-98C VTVM and I’m starting to rebuild that meter as well. I actually just used the HP 410B about 20 minutes ago to do an alignment on a Philco 52-940 AA5 radio. Love that it has a 1 VAC range.
The older I get, the more I dislike "new" stuff. I'd rather spend an inordinate amount of time and a few dollars repairing something, than getting a new replacement and suffering the "new stuff" frustrations. It may also be that I like to check if I can still fix stuff without breaking it. I ran across a small PM motor recently that used the bare copper contacts for brushes. They were worn down to nearly nothing. That one went into the trash.
We just bought a new SUV. By new, I mean a 2004 Chevy Trailblazer. I bought it because the fella had done the head and put new brakes, new ignition coils and tires on it. It runs and drives like a top. It cost 3000 dollars and I need to put a new blower motor resistor in it because speed number 5 doesn't work and I also need to fix the rear window wiper. Ive actually never had a vehicle with a rear wiper. But I can work on it without having to pay the dealer to do a software load for 750 bucks. We are ecstatic, all 4wd works perfect and it's a nice looking truck.
