Rare Rosetti combo overhaul (first timer - help needed!)

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Rare Rosetti combo overhaul (first timer - help needed!)

Postby ollie-wtf on Wed Jan 25, 2017 5:14 pm

Hi all,

picked up what seems quite a rare little combo - a Rosetti with trem.

After plenty research I think the most likely maker is the following: http://www.supersound.org.uk/a10amp.html

the cabinet is completely different, but the controls, and weirdly the handle, is exactly the same.

Im pretty new to working on valve amps, but have started reading around to get a better understanding. My first mistake was to plug it in and play all night long - I only realised after the potential consequences of this. That said, it sounded great. It did have a very audible hiss, not hum.

Order of buisness:

Change the filter caps - its a mullard 50uf-50uf-50uf. Ive found the blue can type at watford valves that seems a good replacement, but, excuse my lack of knowledge, it only mentions 50f twice, not thrice. that said, the number of pins is the same, and one must be a ground on both, so can I assume they are in fact one and the same? It would be nice to get a metal can if a new (old style) one is available?

Change the two electrolytics that form part of the bias along with each resistor. These really are odd items, yellow middle with a red and black cap either end. lord knows, but I assume its sensible to replace these?

I also need a new speaker. The original Elac has torn, either through my own haste, or it went unnoticed. Lesson learnt. What would people recommend? Im not sure whether to track down another elac (10", not sure of ohms yet but I reckon 4) or replace with a modern 'vintage' style? I want it to sound as good as possible, an not sure if the old elacs are rated, particularly once their old?

The on/off switch is built into the depth control for the trem, and someone suggested this could be the cause of the noise too as the mains can leak through (or something along those lines - feel free to explain!) is it worth replacing the switch/pot?

I plan to test all the resistors and caps to see how far theyve drifted, but im less concerned about this. Some of the resistors are odd, they are super thin and pale blue. The rest are carbon comps. The only other 2 caps i can see (aside from the tone one) are long yellow ones that look the shit so hope theyre okay haha.

Valve line up is 2 12ax7s, 6v4 recitfier and el84 output - all original Pinnacle tubes apart from the mullard 6v4.

Any thoughts, guidance, history of said amp, is much appreciated!

I feel this is a great starter project for me, minimal parts, no major problems, and cool vibe with a great sound.

Cheers all!
ollie-wtf
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Re: Rare Rosetti combo overhaul (first timer - help needed!)

Postby stratele52 on Thu Jan 26, 2017 6:29 pm

Another Rosettei here;

http://www.vintageamps.com/plexiboard/v ... 10&t=94497

Do you have shematic ?

Show some inside amp picture
Last edited by stratele52 on Thu Jan 26, 2017 11:06 pm, edited 1 time in total.
stratele52
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Re: Rare Rosetti combo overhaul (first timer - help needed!)

Postby ollie-wtf on Thu Jan 26, 2017 7:48 pm

No schematic. I may decide to draw one up if i get stuck with it. It's pretty similar to the Lucky 7 that the guy in thread you posted has, though the configuration is slightly different. I would hazard a guess that, as he suggests, his is the A6 model with added trem from the A10, whereas mine is the A10.

Interestingly the archaic jack inputs, the pots, the lamp holder etc are all the same, speaker looks it too. The stapled cardboard piece to house the plug is the same on mine too, so these two definitely come from the same factory, supersound.

I'll have to work out how to add pics.

Any thoughts on my above questions?

Cheers!
ollie-wtf
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Re: Rare Rosetti combo overhaul (first timer - help needed!)

Postby stratele52 on Thu Jan 26, 2017 11:04 pm

How to post photo on the forum

1- Upload photo on Photobucket or other

On Photobucket librairy;

2- Choose the photo you want to post.

3- Clic on IMG window and copy

4- Open Fender forum answer window and copy ( the IMG from 3 ) in the window

5- Test with "Preview button" , you should see what all the forum member will see .

6- If ok, press " Submit button ".


:cheers:

Image
stratele52
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