X-P100 'guts'

[eightdigitword]

Opened my X-P100 Pre amp. Thought i'd share the findings:

Big 'X-P100' sticker right over the NU-VISTA etching on both boards, 4 valve locations on the main board missing valves and populated instead with transistors. couple of botch diodes/tantalums here and there on the underside to compensate for the missing valves.

Quite surprised at the amount of components and the quality of inside the unit. Not a Jamicon or polyester in sight. Teapo do feature heavily. Couple of Power PNP Silicon Transistor clearly been running way too hot and trying to destroy my board. Also the 1W Resistors sat between the paralleled PSU caps almost completely burnt out, mental ESR found on the small caps near these.

[eightdigitword]

[nando]

For a comparison between the xp-100 and a Nu vista, I am diggin up this old thread.

This is my modded nu vista right before it was reasembled in the casing.







Bottom pcb.

[nando]

I fitted heatsinks to the transistors on the bottom board because these were running hot with marks underneath the board.

The Nu vista has Jamicons as stock instead of Teapo caps. I replaced all the electrolytic caps with Panasonic FR, FM or Nichicons.
Also replaced the valves with "new" Westinghouse ones.

The big blue blocks replaced the yellow film capacitors.

One 4 pin RCA connectorblock is replaced as well. I had trouble finding the 6 pin blocks so these remain stock.

All connections are resoldered.

[bostown]

Has anyone converted a P-100 to a Nuvista ( or close to a Nuvista?)

[nando]

“How hard could it be?”

Almost all is the same between the two. There are valves in a nu vista, the transformer is in a different casing (don’t know if it’s otherwise similar). But one question is the chip on in the nu-vista. This could be different between them. My nu-vista had a “MF3” sticker on it.

One could argue what the point of it all would be. Would there be a great difference just with the valves?

[eightdigitword]

Shit the bed!!!

just when i thought ill check that forum. no way! the very thing ive been wondering about has been posted. thank you Nando, much appreciated. literally the only two pictures of the inside of a nuvista pre on the entire planet. amazing.

on my xp100:
I too fitted heatsinks to the transistors on the bottom board because these were running hot with marks underneath the board.

I also swapped the big bleed resitors on the top board to higher power with longer legs as they had also scorched the board.

I fitted muse caps in signal, some elna i had spare, swapped the film caps to ERA MKT.

did fit really big film caps to the dc blocking outputr caps but then just removed them in the end.

I'll dig out all my notes and post everything with detail.

merits in fitting valves? My opinion is the same as Nandos. there is no point.

[eightdigitword]

PSU transformer factory details:


┌───────────────────────────────────────────────── ─────────────────┐

│ Transformer TI-66618 │

├───────────────────────────────────────────────── ─────────────────┤

│ PRIMARY SECONDARY │

│ │

│ Bwn 120mm 22AWG   Red 120mm 22AWG 1 74.2V No Load │

│ 230 V o───────────────── ─────────────────o 68.0V 0.10A │

│ █ █ │

│ P2 █ █ S1 │

│ Whi 120mm 22AWG █ █ Yel 120mm 22AWG 2 │

│ 115 V o─────────────────█ █─────────────────o 0 V │

│ █ █ │

│ P1 █ █ S2 │

│ █ █ Blu 120mm 22AWG 3 │

│ │ ─────────────────o 68.0V 0.10A │

│ S01, 130 deg █ 74.2V No Load │

│ │ │

│ Blu 120mm 22AWG │  Vio 120mm 22AWG 5 12.0V No Load │

│ 0 V o───────────────── ─────────────────o 10.8V 0.33A │

│ █ │

│ █ S3 │

│ █ Blk 120mm 22AWG 4 │

│ ─────────────────o 0 V │

│ │

│ │

│ │

│ │

│ │

│ │

│ Primary leads from double insulated cable type UL1672 │

│ │

│ Secondary leads from UL3266 cable │

│ │

│ │

├───────────────────────────────────────────────── ─────────────────┤

│ Nominal dimensions/weight: Mounting method: │

│ (information only) │

│ diameter 70 mm Potted into 105VA Black case │

│ height 27 mm │

│ weight 0.5 kg │

│ mounting excluded │

│ │

│ Pri/Sec leads: + 0 │

├───────────────────────────────────────────────── ─────────────────┤

│ Comments: │

│ 1. Primary resistance: 21+59 ohms │

│ 2. Secondary resistance: 2x40 and 2.5 ohm │

│ 3. Calculated temperature rise at 15VA load: 13 deg C │

├───────────────────────────────────────────────── ─────────────────┤

│ Label: ┌ ┐ │

│ │

│ Toroid International Ltd │

│ P/N: TI-66618 │

│ SL xxxx │

│ │

│ └ ┘ │

└───────────────────────────────────────────────── ─────────────────┘

[eightdigitword]

cut and paste from my notes:
some things are trial and error, whats missing is notes on differences made to sound. some swaps done nothing, some did lots. for the cost of parts and the fun doing it it made me happy. sound is better, although as always it sounded good before!!!!!!


PRE AMP:
SN: 271186 NU-VISTA PREAMPLIFIER ISSUE 02
< 0.007% 20Hz - 20kHz unweighted
< 0.004% 20Hz - 20kHz ‘A’ weighted


Power supply board:
-90VDC - 0v (GND) - +90vDV side, 71Vac (black) - 0v (Green),
0vDC (GND) - +5vDC - =12vDC side, 11vac (blue) - 0v (brown)
Fit fast recovery diodes to both BR
71v AC supply BR swap to DIODE, ULTRA-FAST, 2A, 200V, 15ns, DO-201AD RS: 688-2293. Noisy??
11v AC supply BR swap to Schottky barrier diode,11DQ10 1.1A 100V RS: 395-2487.
R1: 273 Ohm 1W - Burnt, replace with 270R 2W High temp version - fit high off of board Body: 4mm Dia x 11mm
R2: 271 Ohm 1W - Burnt, replace with 270R 2W High temp version- fit high off of board Body: 4mm Dia x 11mm
C5, C6, C7, C8 X 4 1000+uf 100+v PSU caps, bypass with Wima MK (PolyProp) 0.1uf
C5, C6, C7, C8 X 4 1000+uf 100+v PSU caps, Measure DC voltage across caps
Smaller caps on PSU board only supply non audio items - DO NOT UPGRADE unless damaged
C5 measured: 1594 0.28Ohms ESR - bit high, not bad though
C6: measured: 1581 0.14Ohms ESR - not bad
C7: measured: 1615 0.12Ohms ESR - not bad
C8:measured: 1574 0.18Ohms ESR - not bad
MAX SIZE: 34mm DIA X 30mm tall (probably 29mm)


Separate PS enclosure plans:
bigger VA toroid replace with two toriods, 11VAC (min 30VA) & 71VAC (min 100VA)

RS:
208-7071, 1000uf 100v 87mOhm 25 Dia x 30 tall, snap in, Epcos, £3.49
727-1117, Panasonic ECOS2AA102CA discontinued
414-8780,
Now: RS Stock No.790-0222
Digikey: SLP152M100E1P3-ND 0.18Ohm ESR

C11 (8uf 4.8 Ohms) + C12 (8.1uf 4.4 Ohms): 10uf 25v+ - replace with low ESR type. TEMP: nichicon PW(M) fitted 9.6/9.8uf 0.44/0.42 Ohm
C13, 100uf 16v, (measured: 105uf 0.46Ohms) - replace with low ESR type TEMP: Panasonic FM 105 100uf 25v (96uf 0.09Ohms) or oscon sepc
C9 C10 C14 C15: 2200+uf 16+v, bypass withVishay1839 (PolypropP) 0.01uf
C9 C10 C14 C15: 2200+uf 16+v,
C9: 8856uf 0.08Ohms - very good
C10:8940 0.04Ohms- very good
C14:8912 0.03- very good
C15:8912 0.03- very good
2200*4=8800
MAX SIZE: 20mm DIA X 28mm, 1890556 (D18 H25) PANASONIC CAPACITOR, RADIAL, 25V, 3900UF 3900X4=15600
REG1, TO-220 VR: L7805CV, +5v regulator, add small heat sink
Re-solder bad joints
Clean board with Isopropenol

Preamp board:
Service selector switch and volume control: Crackle on output phono's, clean source selector, and volume
copper screen fitted to motorized volume control and source selector
Remove + clean pins and refit PIC16C54 MICROCHIP
PP Film bypass on all signal caps

MJE350G - ON Semiconductor - Plastic Medium Power PNP Silicon Transistor:
TR28: J350 909 Require Heat sinks -RS: 189 - 8303
TR29 :J350 924 Require Heat sinks -
TR128: J350 912 Require Heat sinks - RS: 189 - 8303
TR129: J350 909 Require Heat sinks -
HEAT SINK: TO−225 CASE 77 STYLE 1
VREG:

X2 '47' Ceramics to be replaced with Styrene and glued,
X2 '47' Ceramics to be replaced with Styrene and glued,
X4 '10J', 10pf Ceramics to be replaced with Styrene and glued
X2 '5', 5pf Ceramics to be replaced with Styrene - too small - also not in signal path

C1 + C101: 10uf 63V NP OUTPUT DC CAPS - UBER AUDIO CAPS or use B&W x-over large 10uf polypropylene (Or use polyester ), bypass with 0.1uf film. or remove competency if no DC found on output

C35, C34, C134, C135: 100uf 100v 0.08Ohm measured, Audio caps only
100.8uf, 0.04
101.2, 0.04
99.88, 0.04
99.88, 0.04

(ELNAC-110) - 100uF 100V Elna Cerafine Electrolytic Capacitor  0.03ESR  ELNAC-110   £3.65 each,
NKZ-130 - 100uF 100V Nichicon KZ type, UKZ2A101MHM   NKZ-130   £0.89 each
swapped these around and tried loads of others. to me, Muse caps sounded best.

225J 100v MKT caps x4, 2.2uf
474K 250v MKT caps x4, 0.47uf

[roscored]

Hi guys I have an X-P100 that stopped outputting after a long very easy life. It doesnt get used much, anyway I have wondered if there is a way to fix them or replace the boards etc? There was a electrical smell right it stopped working, so obviously something overheated. Not being very electrically minded I would like to get it working again without spending a fortune. Is there way to do this? Appreciate any and all help thanks. Oh and I live in Australia. Cheers

[eightdigitword]

hey,

everything can be fixed! hopefully it will be cheap.

there are a few things in there that get hot. every xp100 ive seen open has scorch marks in the same place.

It is highly likely one the large resistors on the PSU board (upper) has burnt out.
R1 + R2 in the third picture in the 2nd post. these are 270R 2W each.

next most likely are one of the transistors on the Pre Amp board.
TR28: J350
TR29 :J350
TR128: J350
TR129: J350
MJE350G - ON Semiconductor - Plastic Medium Power PNP Silicon Transistor

there is a hundred things it could be, best thing to do is open it up and have a look. as soon as you open it, it will be obvious what the cause is.

4 bolts on the front, 4 on the back, 2 grub scews in the source and volume knob, all the screws on the back between the rca.

[roscored]

Hi thanks for the 2 responses, I will have to wait and see what happens, even though they cost a lot to buy, when new, they are not going to be worth much now. It sounds terrific but if it is over my budget i will have to look at , dare I say, using my Denon receiver as the pre amp type device though the sound quality will fall dramatically.I will keep you informed. cheers

[nando]

Your welcome, eightdigitword. I to was searching the web for photos of the inside of the xp100 and nu vista.

I still have nog worked on the selector knob because I am a bit scary I might break it even more or can’t put it together again propperly. On the other hand, I have one channel a lot of the time. With a bit of a wiggle it is solved.

[chertseyb]

I too am gob-smacked to find this information in one place, having been searching in vain to find out if an X-P100 can be converted to a nu-vista. Thank you to both eightdigitword and nando for the pictures.

Question still remains about whether it is (a) actually possible and (b) worthwhile?

Is there anyone who has tried it, or has anyone made an A-B comparison of an X-P100 and a nu-vista?

I am contemplating an update to some of the components in my X-P100 and 2 x X-AS100, mainly becuase they are now 20 years old, so information on this forum (and this page) will be extremely helpful. When I eventually get to do it, I will upload a few pictures of the work in progress.

Thanks again to the earlier posters on this topic.

[nando]

You’re welcome.
My guess is that there are not many people having an xp100 and one of the 500 nu vista pre amps to compare.
I think that the gain of the nu vistor tubes will be minimal. The whole amp is almost the same and the nu vista tubes are one of the latest developments of tubes and have low distortion. The distortion is one of the things that make the tube different (better of worse is up to you) than a transistor.

But if you see it as a project, go for it.

[eightdigitword]

AND THEN..... THERE WERE THREE.

(totally agree with nando, above.)

on (a) changing a xp100 to a nuvista: absolutely possible. the board is a nu vista board on both. all you need to do is remove the bodged bits MF fitted on the xp100 to get round the absence of valves, then fit valves. Finding some might be tricky. a data sheet for one would show you what they expect on a board, dbl check if it matches whats there. A pic of nandos board underside would confirm this (dont go to any bother nando), although i am sure there will be nothing there underneath and simply the valves fitted above. although, we would need to confirm the valve buffer transistors are the same type.

on (b) worthwhile: word is MF dropped the nuvista pre amp as the solid state was indistinguishable, not that i am going to believe anything said within the hifi industry!, its likely nu vistas stopped selling and greater profit came from shifting tons of lower cost X units. That said measurements would need to be taken to establish things. Again looking at data sheets for the nuvista valves and the transistors used will tell us a lot on noise, accuracy, harmonics, etc. It may come down to "i prefer the way that sounds" vs that. I suspect what difference there is will not be audible, valves wont last as long, produce more heat, cost more and are less efficient (this is www.efficiency grotto im in right?).

fyi, I have never heard a nu vista

I do wonder how a board made for valves and populated with components for valves can work so well minus the valves with some 5 cent transistors, some diodes and ceramic caps fitted. either the valve version is BS or the solid state is. One must be a compromise is some form or another.

if you do go for it i'll help out in anyway i can with pics, info and measurements, wasever.

On the XAS100. I have pimped both of mine and have the notes on this forum. post on the relevant forum page if you need info.

[chertseyb]

Me again...

Many thanks to nando and eightdigitword for taking the time to post replies to my questions, and for offers to help going forward.

When I first posted I was watching an X-P100 on eBay that was at a low price. My idea was to bring both up-to-scratch with a re-cap and then do the valve conversion on one of them (then keep the one I liked best and sell the other on). I didn't win the eBay auction, but will keep the plan alive. I remain intrigued as reviews of the X-P100 say something like "aside from the nu-vista, the best preamp MF have ever made".

In the meantime I have included the X-P100 in my update plans along with the 2 x X-AS100, and have bought a set of capacitors for replacing the 20yo items in my unit.

More to follow then...

Many thanks

[eightdigitword]

May 1, 2019 14:59:41 GMT chertseyb said:

Me again...

Many thanks to nando and eightdigitword for taking the time to post replies to my questions, and for offers to help going forward.

When I first posted I was watching an X-P100 on eBay that was at a low price. My idea was to bring both up-to-scratch with a re-cap and then do the valve conversion on one of them (then keep the one I liked best and sell the other on). I didn't win the eBay auction, but will keep the plan alive. I remain intrigued as reviews of the X-P100 say something like "aside from the nu-vista, the best preamp MF have ever made".

In the meantime I have included the X-P100 in my update plans along with the 2 x X-AS100, and have bought a set of capacitors for replacing the 20yo items in my unit.

More to follow then...

Many thanks

No worries. They come up frequently enough.

I do wonder how many actually compared the NV to the xp. I think the 'legend' and RRP of the NV made most simply assume it was better.

Most owners never opened them up. Wonder what they would have thought if they knew the insides were 98% identical.

I'd love to know what someone thought comparing the two. Whether its worth the hassle and cost is another debate.

[nando]

If I remember correctly the reviews of the xp100 were very good. So one would think there is not a lot wrong with it. Maybe the nuvista is better or just different but both seem to be recieved well by the media and public alike.