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How to Restore Dynaco PAS Tube Preamp Cap replacement Power supply upgrade SDS Labs kit
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- เผยแพร่เมื่อ 7 ส.ค. 2024
- Is your Dynaco sick, weak? I have went thru this process many times. This video will guide you thru the process of restoration. Installation of the SDS Labs Cap board and D-Lab's AC Relay switching. I have a new integrated circuit board in the works. Soon to be released as a kit and custom install at my shop. Sorry for the delay in video posting. I have been swamped with the day job issues, then race to get something off the bench. Keep in mind, this is just my method of installation.
OK, you are the tube amp master, and I am the guy studying the repair of tube amps. I have been watching Uncle Doug's videos for several years. I am not questioning what you are doing. Uncle Doug would I believe replaced the line cord with a three wire and grounded the chassis. He would also add a line fuse. The fuse you installed is only for the relay. I have been in the electrical field all my life and am a ham radio operator. I retired a few months ago and I am pursuing electronic repair.
I watch your and Uncle Doug's videos in pure amazement. I have no clue what either of you are talking about and no idea why I follow these videos because it's all Chinese to me. Still cool to watch. Perhaps I pick up a little here and there. 👍
Sweet. I have my dad's Dynaco ST70 amp, this pre-amp, and the tuner, that he built from the kits when I was a little kid. Along with an Empire Scientific turntable, and a pair of sand filled 3 way Wharfdale speakers he used with them. I'm planning on restoring every thing, and I'll definitely use your relay idea, and probably get the kit from you when I'm ready. You do very nice work. Please show more of the Dynacos!
Terry, your videos are always concise and clear. Worthy watch everytime!
Look forward to more Dynaco stuff!👍
Hi Terry, I believe a couple of folks already queried same, but did not see response. Would you be so kind as to let us know what relay you're using. Thanks!!
God Bless and Protect you and your wonderful family. Thank you for sharing your wisdom with us.
Hello,
Just wanted to start by saying I really enjoy your TH-cam videos. They have really helped me alot. I am new to the vintage audio repair game and like to get advice from your videos. After watching your video on the PAS-3 preamp recap I decided to use the SDS Labs cap board that you used on a Dynaco I'm repairing. I was a little confused with the instructions that they provided because It didn't match the board that was sent.
I noticed that the board that I got was the same as the one in your video. I have figured everything out except the J1, J2, J3, and J4 connections. I am assuming that the J1 and J2 connections that say blue in the instructions are the blue transformer wires. J3 and J4 say they are lamp wires. I am not sure where these are supposed to be connected to the preamp.
Any help would be greatly appreciated.
Thanks again,
Al Kuhn.
p.s. Keep up the great work on your TH-cam videos.
That was so smart .i wondered and wonder hope to fix the on /off small swtch
Love dynaco stuff. I'd like to see more.
Now that is a great upgrade for a preamp! Like the addition of a relay for the switched outlets, designers should have thought of that back then. More please
Terry when you get some time.🍷🍷🍷
Compact relays for this application did not exist then. Audio Research used a large relay on the SP-8, and this was the early 1980's. The PAS original design dates from 1960 or so.
Thanks Terry, good idea with the PCB! Peter
Nice mod. Relays are fun!
Terry, I might be interested in getting one of those boards if you decide sell them. A couple years ago I installed one of those SDS replacement boards but I'm still having trouble tracking down some hum in the unit and wondering if it may be that fuse sitting close to the output wires. Never even occurred to me. I may have to reopen and see if moving the wires away from the fuse has any affect on the hum. Great tip on relocating the fuse location.
Yes Sir, That might be.
Let me know if that solves the issue and I will make the changes to my board before the final design. Thanks, TD
back when the pas3x was first made the current in an average wall socket wasn't as high as today
Hey Terry, that Multimeter needs some cleaning! :)
Yes and so does my undies
I heard some of these boards when installed create more hum on one channel than another. Maybe the wiring needs to be redressed. I'd prefer to keep my PAS stock and re-stuff the original filter can if needed. But, as usual, your mileage may vary..
Do you have a link or where did you purchase the relay? I take it it's just a 125v, or 250v 8a, relay with a 120v coil.
With the power supply caps replacement from SDS audiolabs, when replacing the 12x4 rectifier with the diodes option is chosen, am I correct that all that I do regarding 12x4 tube and socket is attach the two red transformer wires. I don't see anything else in the instructions in that regard. Do I leave current wires in place and remove the tube. Sorry I am kinda a newby. Also, spec info on the switching relay would be appreciated. Thanks for the vids.
Is the circuit board you speak of available yet? If so I'd love to purchase one. If not, please put me on the list and notify me on how I can order one. Thanks!
👍
Hey Terry, were you going to change those coupling caps out in the PAS-3 like you did in the ST-70? I have a PAS-3 I acquired 10 years ago for my Heathkit W-5M mono block amps. Someone before me bypassed the selenium rectifier with silicone diodes and did not use any dropping resistors. I never run my amps through the preamp switch, I have them plugged into a Pangea Quattro Premier power strip and unplug them from the wall. Have you thought of putting a zener diode regulator in the circuit for the 12.6 volt filament power? Would that be beneficial?
Please offer a circuit board only option. I like to specify my own parts.
There is a circuit board option, just go to SDS Labs website. www.quadesl.com/refurb/refurb_dynaPAS.html or contact:
Sheldon Stokes
5600 Montano Road NW
Albuquerque, NM 87120
(505) 897-1305
stokes@spinn.net
www.quadesl.com
BE VERY CAREFUL of TRIODE Electronics, there have been many reports these last two years of non -shipment of orders, customers not being refunded their non-shipped orders and / or over 3-5 month shipping times. Uncle Doug absolutely refuses to do any more business with them and warn his viewers about them too. Audiokarma has a page about them and so does the BBB. Latest complaints I've seen are from late 2019.
Terry, I have a Dynaco PS-1 and a st 70 swet up my step day built in 59-62???? I have it and the original manual and it has Mullard Power Tubes aND RECTO TUBE AND TELE-FUNKEN PRE AMP TUBES.. IT WORKED 100% PERFECT THE LAST TIME IT WAS USED IN ABOUT 93... ANY RECOMENDATIONS BEFORE I PLACE IT FOR SALE?? I ALSO HAVE HIS THORENES TD-121 TURNTABLE...... Whoops, didnt see the caps , sorry
Hey Terry love your channel and videos.you should go on eBay and look at the tube preamp pedals they have on there that's modeled after Marshall tube amps and fender and all other tube amps.they are making a killing on those pedals.id love to see you do a video making a pedal like that.you could make some good money on those pedals.cheers Terry.be well
I found a fully rebuilt st 120 with new boards transistors tip mod and van alstine power supply. Would you recommend?
I have a eico st-70 that I rebuilt.
I have a nostalgic soft spot for EICOs; my late Dad hand-wired an HF-81 kit in 1959 that I fondly remember from my childhood in the 1970s. Sadly it is long gone, last seen in a move in the 1980s.
That line is fused by the 24 awg wire used for wiring it.
The line cord is 18ga
My old Stereo 70 is looking grubby. They make a stainless chassis for it. Do you think its worthwhile to go that far?
Of course it's worthwhile to go that extra mile. Those SS chassis looks great! I believe that they cost around $100, but look well worth it, especially if you're restoring that vintage Dynaco ST-70 amp. I will building a new ST-35 this coming spring along with the custom biasing circuit board add-on for it. Terry at D-Lap never hardly ever answers any questions here or responds to comments for some unknown reason. Think about it... circuit boards are "circus" boards. Resistors are "resistoroids"... sheesh. if he were more serious about his videos and actually do full videos of the circuits he works on I would probably be more attuned to watching all of them. I watch Uncle Doug a lot and when it comes to knowledge of basic circuits and explaining their functions and such... no one comes close to Uncle Doug. Uncle Doug basically deals only with guitar amps however. Uncle Doug has more than double the subscribers and his dry humor is truly unique. I used to watch a little of Brad the Guitologist but his constant cursing and such was a turn-off. If one cannot express themselves without resorting to cursing then their vocabulary is extremely limited.
Right???, Uncle Billy.
Other than convenience, is there any other reason why the rectifier tubes are kept instead of replacing them with diodes?
I believe most folks like the rectifier tube because it has a slower warm-up time and provides more swampy bass and such. Diodes are instant-on and can shock the output tubes with really high surges of B+ voltage at the very beginning. That's why high voltage reservoir caps are used in many circuits to take that high surge.
the power cord is also bad
D Labs...I sent you 2 emails and you never returned a response.
I will take a look
I sent you 2 very nice emails needing help with something about a month ago. That’s the way you treat your subscribers?
UNSUBSCRIBED!!!!!
Hello Terry. Have you thought about creating a separate channel for your audio and your ham/vintage radio equipment repairs/restoration? It may just be me of all your subscribers but I have little to no interest in audio equipment. I am thinking of unsubscribing and will perhaps just check in from time to time as a non-subscriber. Just a thought.