RocketRick

Well what does "low mu" mean? Also, two test in the 40's while the 3-mica one gives test results in the 100's. Why the diff? And thanks for your kind attention and advice..Your the man!!

OK..here ya go Myles- I guess I need to read a primer on tube testing.. 2-Marched Premium 12ax7: Fully tested on a calibrated TV-7 conductance tester at 43/47 and 47/49 where 32 is good. Originally sold and labeled for the Sanborn Company. ======================= 2-Matched RCA 5751 tubes (lo mu 12AX7 ECC83): black ridge plates, 2 mica spacers, extra support rods between mica spacers and halo ring getters at the tops. Tubes appear identical in construction! Hickok TV-7B checked @ 42/41 39/44 ==================================================== 2-RCA 3-Mica Black plate 5751/ECC83 Test at 118/130, 120/130, on a EICO 667 Ttube tester.min:60 ==================================================== 2 NOS Mullard 12AT7WA CV4024(12AT7 ECC81): These are the low noise CV4024 m8162 British Military version of the 12AT7, manufactured by Mullard in Mitchum, Great Britain, not the inferior Mullard re-issue tubes currently available! Coded '654 R4D3' (Mullard Mitchum, 1984) Pairs selected by factoring in both IP and Gm. Gm tested at 3600/4500, 3900/4900. Min 2500, average new 3850 mho. IP (plate current) 3.8/6.6, 4.1/6.4. Average new 3.7 ma. Fully Tested on a Hickok 539C tester and guaranteed.

Myles; Whelp I got these tubes. Not sure how I know if one is better then another tho. 2-RCA 3-Mica Black plate 5751/ECC83 2-Matched RCA 5751 tubes (lo mu 12AX7 ECC83) 2- Matched Pair premium plate 12AX7 2 NOS Mullard 12AT7WA CV4024(12AT7 ECC81) Most gave some readings for the tubes but not sure what that means. I think the numbers mean the plate voltage but some of the numbers are large and some are small..Must be in millampearage or millvoltages and some must give the whole number.. Kinda confusing..I'm assuming the higher the numbers the better the tube? Also, depending on the amp, I'm assuming I want to check the tubes and see if they are within the operating range for each particular amp.. Can you clarify the meaning of the numbers they provide using there test equipment? thanks

Myles, I've been searching for some tubes . I noticed some of the black plates are 2-mica and some are 3-mica..What's the real diff between those? thanks

Thanks Myles your the man.. :}=

Myles, I recently did a mode for pins 1-8 connection on the Mesa Boogie amp. I then used DeOxit on all the switches etc. Do I need to use some other sort of "moving contact lubricant" after using the DeOxit? thanks

Well the Marshall heads can go to 16 but the Mesa only ouputs to 8-ohms. However, it seems to play just fine into the 1960AX 4x12 16-ohm cab. thanks

Preferred speaker combo.. Myles I hope to try diff configs and figured out that I can do with various speaker hook up combos. Using 4 8-ohms speakers one can do series first then parallel or vice versus. Which config is preferred as per the amp? thanks

OK thanks a heap

Thanks Myles. Now I'm not saying your wrong but I did get different opinions from several users and Mike Bendinelli. I talked to Mike Bendinelli, who help build and test the amp in 1984. He said it was just fine to do the mod and use the El34's. He also said some of the vintage Sylvania and GE tubes already has those pins connected so I wldn't have to do the mod but I can't find any yet. Anyways, I'm inclined to do the simple mod and try it out but it never hurts to get another opinion.

Myles, I plan to do a small mod on my Mesa Mark IIc+. I have two questions; I will solder a piece of wire to connect pins 1 & 8 on the outside output tubes sos I can use EL34's in the 2-outside tubes. 1. Do you see any probs in doing this? I've seen your comments and insights into many different tubes. 2. Can you make any recs for diff tubes for me to try in the preamp and the output sections? thanks rick

My tech here said I will loose 1/2 the power. He said the best thing is to wire the speakers so that 2 pair are in series and then each series pair in parallel for a total of 8-ohms. That way I can use the cab with all amps.

I'm wondering about making a device I can use to play the 16ohm 1960AX cab with the 8oum output frm the Mesa amp. Place a 16-ohm resistor in series with the amp = 8-ohm load. Only thing I see is the ALL of the load won;'t be reactive. Ideas...thoughts? Dumb or?

Myles, Can one take some of the tubes out of say a Marshall JCM 800 100 watt amp and make it do 50 watts w/o messing things up? Thanks Rick

Thanks Miles. He said he has several online sources for parts like that but I'll mention that place to him. I think he said a replacement wld be abt $60. Not sure the old 60watt UniVox head is worth the trouble but it is an older type unit and I fig for a few dollars, I aught to be able to get some usuable recording sounds from it. Oh, he did talk about measuring the resistance or the windings and how the Z changes depending on the freq. He's an old hand.. Rick

Myles, I had the amp checked. The tubes are fine and the tech said the output transformer needed to be replaced. He said it was causing distortion and low output. What does it do and how is it tested? thanks Rick

Myles, I had the amp checked. The tubes are fine and the tech said the output transformer needed to be replaced. He said it was causing distortion and low output. What does it do and how is it tested? thanks Rick

Thanks again Myles. Your a gem.. BR ====

Myles, Here's the pic of the back on the Univox head. It has 2 large tubes a row of smaller ones to the right. Dont guess you need the kind? One weird part is a metal box attached to the inside of the back cover with 2 wires that plug into inside. Never seen that before. thanks for your time and expertise. http://i179.photobucket.com/albums/w292/Bluedog_bucket/Univox_back.jpg

Myles. It is a tube amp. I read some print on the back and it's output is 60 watts. also, beside the model no is the word Lead so i guess its for guitar but i use it for bass. wonder if that wld hurt it? Here's a pic of the back.(hope the link to the pic works) http://file///C:/Documents%20and%20Settings/Rocket.RICK.000/My%20Documents/Music/My%20Guitar%20Pics/univox_back.jpg

Myles, I got this(see pic) in the mid 80's and its mostly sat since then. Just getting back into it. 1. Its 200 watts but Im not sure if its a bass head or a guitar head. 2.The knobs are scratchy & intermittent. Shld i take that elec spray cleaner and spray them while rotating them? 3. I like the sound but was wondering if the tubes shld be replaced since its so old. Any other info/comments abt it you can provide wld be helpful also. thanks for your time. BR http://i17.photobucket.com/albums/b79/RocketRick/Uni-Vox.jpg