RCA/Victor Strato-World Radio

Recently purchased from an antique store. The tag said “powers on” but I haven’t plugged it in yet. It needs an inspection, very likely full replacement of the electrolytic capacitors. I do not yet have an oscilloscope so the
full radio alignment may have to come later.

This radio was made in 1953 and uses small bottle tubes for the amplification. It was intended to be able to run off of line voltage or a battery.

More to come…

Mesa/Boogie Fifty/Fifty Deep Mod

My Fifty/Fifty, SN FF-6446 had the deep mod installed at the factory. Lucky for me I didn’t have to do anything.

Details on the mod preserved below:

Granger Amplification sells a kit for this mod;

https://grangeramp.com/product/mesa-50-50-power-amp-modification-kit-2/

Preserved from: http://forum.grailtone.com/viewtopic.php?t=55963

Images removed.

Post by Triaxstasy » Sun Sep 11, 2011 3:45 am

Since I did it to mine and there´s not too much info floating around, here´s a detailed instruction to the 50/50 Deep Mod:

The blue text is copied from the original MB tech document for the modification:

before the mod:

assembled and wired 6-20-1990 :D the board says “Mesa 50/50B , 1989”

MODIFICATION INSTRUCTIONS FOR FIFTY/FIFTY

When the Fifty/Fifty was first introduced, it was designated as the companion poweramp for our Studio Preamp. Now, with the advent of the TriAxis Programmable Preamplifier, we are offering a single mod which greatly improves the compatibility between the TriAxis and the Fifty/Fifty by adding warmth and fullness plus a little additional power. Although the procedure is simple and requires less than one hour, you must REFER THIS SERVICE TO A QUALIFIED TECHNICIAN.

1. Bolt the filter choke to the side of the chassis near the input jacks. It is not necessary to drill holes. Just run the pair of 8-32 screws through the cooling slots and mount the filter choke horizontally. NOTE: To ensure proper grounding, “metal-to-metal” contact must be made. Scratch a little paint off the inside of the chassis where the hardware mounting the choke will make contact, and use the star lock washers between the chassis and choke. The best location is in the third row of slots up from the bottom, farthest slot toward the rear. Thread the nuts on the bolts and – before tightening – slight the choke toward the front of the amp as far as it will go on that rear slot.

2. Solder the two orange choke leads across the 1000 ohm, 7 watts sand block resistor, R501, one lead to each end. (I simply unsoldered R501 and put the choke leads in its place)

3. Replace the cathode resistors and capacitors at V1, the 12AX7 tube nearest the input jacks. These four parts are lined up next to each other just to the right of V1, as seen looking from the front towards the inside rear of the chassis. R202 and R203 each become 2.7k and C5 and C6 become 15.6µF/35v. Be certain to align the “+” ends with the “+” sign on the circuit board. original:

modified:

4. Look at the 8ohm speaker jacks and locate the red and orange wires. Unsolder these wires and add a .003µF disc capacitor between each wire and the jack where it was originally attached. Glue the capacitor bodies to the back of the jacks.

EXTRA MOD INFORMATION

If you have one of the early Fifty/Fifty´s and it has a noticeable buzz in the background, here is a very simple cure:

1. On the V1 tube, remove pins 2 and 7 (counter-clockwise from the gap). These can be difficult to unsolder so it´s ok to clip off pins 2 & 7 just flush with the PC-board. Be sure to leave enough of the pin material so you can bend and solder to them. Then unsolder the grey and white wires which come from the Level Controls to the circuit board just below the cathode parts. Bend up the remaining pieces of the pins from the socket and solder the wires to them directly. The white lead goes to pin 7, the grey goes to pin 2. Lift C18 .1/400v cap for easier access.

white=black grey=red

Required parts: - 1 Filter choke (I used a 125C1A from TAD @ 25€) - 2 .003µF disc caps (I used Orange Drop 716P) - 2 2.7k resistors - 2 15.6µF/35V caps

edit: Since I had the complete board out of the chassis I went for “major overhaul” and replaced all filter caps ((4x 220µF/350V; 2x 50µF/100V; 1x 33µF/500V), all Orange Drop (there were 715Ps in which I replaced with 716Ps), a couple of resistors and all old ceramic tube sockets with new high-quality Belton-Micalex ones. Mine was originally a 110V US Version so I got in contact with a small electronics workshop here in Germany who does custom power and output trannies and had them wire a customized 220V PT to the specs of the original (for 80€). It also has a higher quality WAGO connector. I also unsoldered all original wiring and rewired the whole amp with new 18gauge high-quality silicon wire and shielded wires for input and Volume. All 4 pots where replaced with new Bourns pots. The small blue/white trimpot is a modification to the Boogie-typical fixed-bias….guess what?!? It´s now adjustable :-) (Thanks @ Crane !!!!) The original fixed bias was set at about 21mA…ooooh, icy cold :nono: It sounds waaayyy better at about 35mA….

The final result is now the quietest tube power amp I have ever heard….and I simply love it!

1950s Smith-Corona Skyriter Typewriter

Superficially cleaned and lubricated. Need to learn how to safely do full disassembly for a more thorough cleaning and lubrication. Keys that were sticking no longer stick. Ribbon was replaced previously.

The finish has some blemishes on it that I am unable to remove through normal cleaning. I may need to contact someone who specializes in cosmetic restoration to get this thing looking like new.

Superglued felt pad protecting the keys back into place.

It is missing the left shift key. A replacement needs to be found or made.

Mesa/Boogie TriAxis Refurbishment

TriAxis Serial Number: T0111

Modifications: Version 2 with Phat Mod

Problem 1:

When I received the unit it needed new tubes. After installing the new tubes the unit sounded like it had lost all power. The output was much too low and it sounded like there was a wet blanket in front of the speaker cabinet.

Fix 1:

Inspected wires connected to the TX4 board. One of the wires (red, closest to power input) had become disconnected. Reconnected the wire. DONE

Problem 2: After playing for some time the unit will become “confused” and switch patches at random, the lights on the display including the 7-segment displays will flicker at random. When the unit comes back to its senses the patch I’ve programmed are lost.

Fix 2:

Replace optoisolator. Sources on the internet identify the optoisolator associated with the MIDI circuitry to be the culprit.

The wrong part was installed (6N139) which caused erratic MIDI patch change behavior and in some cases no response from MIDI input. Installing the correct part (6N138) resolved the issue. DONE

Problem 3:

Unit is over 20 years old and requires preventive maintenance.

Fix 3:

Replace all electrolytic capacitors. Inspect all point-to-point wiring. NOT DONE

Capacitor List:

BoardPositionTerminationCapacitanceVoltage
TX2CNear FL11Axial3300uf10
TX2CC3Axial4700uf25
TX2CC4Radial1000uf25
TX2CNEAR CR2032 BATTERYRadial100uf6.3
TX2CC33Radial100uf6.3
TX3AC1Radial100uf6.3
Rear PCBNear Q5Radial1000uf25
Rear PCBNear Q5Radial1000uf25
Rear PCBNear Q5Radial1000uf25
Rear PCBNear Q5Radial1000uf25
Rear PCBNear DVAxial3300uf10
Rear PCBNear MainsAxial30uf500
Rear PCBNear MainsAxial30uf500
Rear PCBNear MainsAxial30uf500
Rear PCBNear MainsAxial30uf500
Rear PCBTo Upper Right of IC3Radial1uf50

Digikey BOM:

Manufacturer Part NumberManufacturerDigi-Key Part NumberQuantityUnit PriceExtended PriceDescription
6N138Lite-On Inc.160-1795-ND50.81$4.05OPTOISO 5KV DARL W/BASE 8DIP
SN74LS14NTexas Instruments296-1643-5-ND50.67$3.35IC INVERTER SCHMITT 6CH 14DIP
UKA0J101MDD1TDNichicon493-4618-1-ND30.41$1.23CAP ALUM 100UF 20% 6.3V RADIAL
UKA1E102MPDNichicon493-15328-ND51.08$5.40CAP ALUM 1000UF 20% 25V RADIAL
MAL202116472E3Vishay BC Components4328PHBK-ND14.17$4.17CAP ALUM 4700UF 20% 25V AXIAL
MAL202114332E3Vishay BC Components4012PHBK-ND22.77$5.54CAP ALUM 3300UF 20% 10V AXIAL
UDB1H010MPM1TDNichicon493-13355-1-ND10.62$0.62CAP ALUM 1UF 20% 50V RADIAL

Parts harder to obtain:

OPA2604AP low noise OP AMP replacement must be sourced from Chinese vendors on eBay.

VTL5C9 Audio Opto-Coupler only manufactured by Xvive in China.

There is a US based retailer for VTL5C9

http://smallbear-electronics.mybigcommerce.com/photocoupler-vactec-vtl5c9/

Mains filter capacitors:

https://www.tubesandmore.com/products/capacitor-sprague-atom-aluminum-electrolytic

Mesa/Boogie TriAxis Phat Mod Reversal

NOT DONE

 

Preserved from https://forum.grailtone.com/viewtopic.php?f=5&t=59839

 

Introduction

I’m not what you would call an active member of the forum but since I got most of the information for this mod from here I thought it would be nice to give a little back to all of you. Let me start by saying that this mod is really simple but the Triaxis is not. As a matter of fact it’s a fragile and complex unit. This is why I don’t encourage anyone without previous soldering experience to perform the mod.

The other thing to say would be that you should pay attention while working on any tube device since there may be lethal voltages and all that crap. But if you are confident enough to work on a Triaxis you probably know what you’re doing and if you don’t maybe you shouldn’t be such a cheap bastard and send your unit to Mesa.

Now that we got that out of the way…let’s fire up that soldering iron and start taking out the bazillion screws this thing has Initial information

I’ve seen two pieces of information regarding this mod one is this picture and the other one is a little text saying pretty much the same. I’ve also read that it seems to be some degree of inconsistence between boards so I took this schematic from tubefreak.com and opened up my unit. I checked every part of the hand written schematics and it was almost exactly like it was on my Triaxis. The only difference was the order of C12 and R46 but since they are in series it doesn’t matter. So from what I could gather the instructions for the mod make sense.

The mod takes place within the TX4 board which is the one Mesa added specially for LD1 Red and doesn’t alter the other modes in any way.

I can tell my unit is V2 because it shows 2.0 all over the display on startup, the serial number is 62XX and it has MIDI continuous control capabilities.

I can tell is a Fat mod because, aside from sounding like poop on that mode, the factory presets are as follows:

Preset 10: 6.0 6.0 7.0 8.0 2.0 0.0 5.5 2.0 0.0

Preset 11: 6.0 6.5 7.5 7.0 5.5 0.0 4.5 5.0 0.0

I should mention that it’s impossible to get a decent tone from LD1 Red as it is. Yes, it sounds fat, but it’s a loose and undefined kind of low end. So if you find your unit to behave this way on that mode you probably want to get rid of the Fat mod. Sound Differences

Before you even consider performing the mod I would like to state that after I did it to mine it sounded amazingly tight and focused but there is an overall fizz factor that’s hard to tame. I think this is the stuff that made them create the fat mod in the first place. It is the same kind of fizz that you can find on a JCM800 and it’s not that easy to eliminate. Either way I think Mesa’s “solution” was quite poor. I’ve worked on a lot of Marshallesque designs so I know a thing or two about this kind of distortion and there are a couple of improvements I will be trying out in order to make this mode fully controllable but for now let’s focus on undoing the Fat mod. If you still want the original “Recto” sound keep reading. My opinion is that it is way more usable than the Fat mod but you may differ. Mod Details

The mod can be separated in three parts, the first one changes the filtering between the first and second gain stages. The second one alters the tone stack section and the third one change the effect of the mid and bass EQ settings.

Since the unit is crammed inside and the TX4 Board is really close to the top cover you should make sure the new caps don’t stand up too tall. There’s no need for measuring, just compare their height with the existing components. That alone will ensure proper clearance.

These are a couple of pictures of my unit’s TX4 board as it was when stock.

Looking at the first picture, locate the three places where the mod is done. Part one is on the top left corner of the board. Part two is on the top right corner and Part three right in the center of the board. PART ONE Replace R45 with 330k Replace C22 with 47p R46 = 82k C12 = 1n The following schematic shows the difference between my unit and the Recto version. These pictures show the steps… PART TWO Replace R9 with 120k Replace C6 with 1n C5 = 1n R44 = 33k C6 was 1n on mine but that’s not the case with all the units. I removed it anyway to show where it is.

Difference between my unit and the Recto version. Steps…

Notice I used a 3k3 resistor for R44 instead of the correct 33k value. The original value is 33k.

PART THREE Replace R33 with 1M Replace R34 with 10k Just two pictures for this one…

THATS IT!

I was going to make before and after sound bites but I got carried away and forgot to record the before one…sorry guys

Hope this info helps Last edited by Inkomodo.Dragon on Tue Oct 01, 2019 10:23 pm, edited 3 times in total. Top