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Thread: Lentek Head Amp - Naked!

  1. #1
    Join Date: May 2008

    Location: A Strangely Isolated Place in Suffolk with far away trains passing by...

    Posts: 13,053
    I'm David.

    Default Lentek Head Amp - Naked!

    As part of a prep to create a 9V external supply for this head amp, I thought I'd take a deeper look and see if the circuit could be exposed.

    Success.....



    The little pot is just a cover and was glued to the sides of the inner tray. The board was also attached via a sticky pad to the base of the tray and the adhesive had worn out -



    Here's a closer look at the board -



    For copyright (?) reasons, any printing has been removed from the transistors, but hopefully the pics can tell someone the values of the very close tolerance (for the period) transistors used.

    As for the caps, the outer tantalums are 6.3V 47 (uF?), the inner ones are 16V 10 (uF?), the two purple topped flat caps are n22's and the three little flat red ones have black and orange dots on (black at top, orange bottom right).

    Am I right in thinking that the tants might be the cause od the slight "solid state brightness" this unit exhibits (and has always done from memory?). I don't know enough to know..

    I've fitted a PP3 socket to the existing plug, which I've repaired, and taken the leads out through one of the screw holes (screw wrapped and placed in battery tray for posterity). This should make things possible to put back to original easily.

    By the way, I've measured the voltage of the extra long life Alkaline PP3 I fitted and on my digital volt-meter it measures 9.14V. This makes me think that the regulator output shouldn't be set to more than 9.5V I think, unless anyone recommends differently

    Dave R

  2. #2
    Join Date: Jul 2010

    Location: North Cambs UK, Earth, Sol, Orion - Cygnus arm of galaxy

    Posts: 11,193
    I'm MadeOfDeadGiantStarsThatExplodedEonsAgo.

    Default

    Mmmm, a few things there could be moddified

    First up set your regulator to 9 or 10V, it won't be a problem...

    If i was you & i owned this head amp i'd change all the resistors for decent ones. The n22 capacitors i'd change to 220pf (which is what they are) polystyrene caps. Pity i can't see the circuit drawn out so we could establish exactly what the tantalum caps are doing precisely

    The transistors look like TO5 jobbies, i'm guessing that they'll likely be medium power & rated at about 1Amp. These kind as well as TO126 trannies are often used in MC pre amps simply because they have a lower noise floor.

    Perhaps if you could get a decent shot of the PCB track side square on i might be able to draw the circuit out & then you can modify to your hearts content
    Bests, Mark



    "We must believe in free will. We have no choice" Isaac Bashevis Singer

  3. #3
    Join Date: May 2008

    Location: A Strangely Isolated Place in Suffolk with far away trains passing by...

    Posts: 13,053
    I'm David.

    Default

    I've put it all back together now and couldn't tilt the board any more without removing some wires

    I thought the resistors were 1% ones, both metal film and a few carbon ones. I can certainly open it again sometime and try to get better shots (I don't have an enthusiasts camera I'm afraid). Poly caps are fine to change to, but what are the ones with dots on in value?

    Am I being picky regarding the tants, or are they really good (I have "memories" of Naim gear stacked to the gunwhales with 10uF tantalums )
    Dave R

  4. #4
    Join Date: Jul 2010

    Location: North Cambs UK, Earth, Sol, Orion - Cygnus arm of galaxy

    Posts: 11,193
    I'm MadeOfDeadGiantStarsThatExplodedEonsAgo.

    Default

    There are much better caps out there that'd fit in place of the tantalums. Sanyo Os-cons spring to mind & they'd be a similar size with those voltages & capacitances you quoted

    E2A:- Those 1% resistors you are refering to happen to be 20% tolerance (red band at the end) & they are most likely carbon Sorry i have no idea of the value of the dotted caps...
    Last edited by Reid Malenfant; 11-08-2010 at 18:14. Reason: added value
    Bests, Mark



    "We must believe in free will. We have no choice" Isaac Bashevis Singer

  5. #5
    Join Date: May 2008

    Location: A Strangely Isolated Place in Suffolk with far away trains passing by...

    Posts: 13,053
    I'm David.

    Default

    Red band at the end is +/- 1% - i.e. 2% I thought - I checked on some charts again to make sure...

    I'm not going to go totally mad here, but caps will definitely be looked at at some point. Thanks for advice regarding supply voltage too.
    Dave R

  6. #6
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 47,745
    I'm AudioAl'sArbiterForPISHANTO.

    Default

    Hi Dave,

    Most interesting, and well done for opening up the old girl! I sense some future 'tweakage' shenanigans

    I'll be following this thread with interest......

    Marco.
    My system:

    Modified Technics SL-1210MK5G/Mike New high-precision bearing & base-plate/Mike New ETP platter/‘YNWaN’ magnetic record clamp with Nagaoka GL602 crystal T/T mat/Paul Hynes SR7EHD PSU (plus regulator modules)/DCSXL pure-silver DC lead with Yaeger (low-impedance) connector. Ortofon RS212D tonearm (fitted to 'Speedy Steve' custom-made Ebony armboard). Yannis Tome 423.5 Phono Silver Litz tonearm cable (fitted with Furutech CF-DIN(R) and Eichmann silver Bullet Plugs)/Ortofon SPU Royal GM MKII cartridge. Other cartridges: Denon DL-S1 (fitted into an AT MG-10 headshell with AT-6106 Quattro Hybrid lead wire), Denon DL-103 (with FR S/3 headshell), US-original Shure SC35C. Audiocom-modified Sony X-777ES/DAS-R1 transport/DAC. Nakamichi BX-125E. Heavily-modified Croft Charisma-X preamp. MC head amps: Paul Hynes with SR5 PSU. Nick G modified Lentek. Tube Distinctions 50W Class A (P/P) Copper amp, with cryo-treated Tung Sol KT120s. 'Lockwood Major' speakers, using 15" Tannoy Monitor Golds, modified with bespoke crossovers. Other speakers used: Celestion Ditton 66 Studio Monitors. Stands: Mana Acoustics (non-magnetic stainless steel 'clones'). Cables: Mains Cables R Us 'Ultimate' power leads (using Furukawa EE/F-S 2mm & 2.6mm solid-core cable), with Furutech FI-50 IECs and FI-1363R 13A plugs. Also Supra LoRad 2.5 (for PH head amp). Stereo interconnects: Klotz MC5000 high-grade microphone cable/MS Audio Starline Rhodium-plated plugs. Oyaide FTVS510 digital interconnect with WBT NextGen-0110Ag RCAs. VDH 'The Wind' Hybrid II speaker cable. Mains block: Mark Grant 6-way, modded with Furutech FP-1363R sockets and Furukawa cable. Tube Distinctions digital noise filter. VPI HW 16.5 record cleaner.

    "Experience without theory is blind, but theory without experience is mere intellectual play" -- Immanuel Kant.

    Digital music: do you remember your first ever download? Unlikely... But you'll probably remember the first record you bought! Forget 'virtual music': VINYL IS FOREVER...

  7. #7
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 47,745
    I'm AudioAl'sArbiterForPISHANTO.

    Default

    Btw, here's an interesting thead about the Lentek on Lenco Heaven:

    http://www.lencoheaven.net/forum/index.php?topic=2317.0

    And one here: http://www.thecrossovernetwork.co.uk...ep-up-for-sale.

    Marco.
    My system:

    Modified Technics SL-1210MK5G/Mike New high-precision bearing & base-plate/Mike New ETP platter/‘YNWaN’ magnetic record clamp with Nagaoka GL602 crystal T/T mat/Paul Hynes SR7EHD PSU (plus regulator modules)/DCSXL pure-silver DC lead with Yaeger (low-impedance) connector. Ortofon RS212D tonearm (fitted to 'Speedy Steve' custom-made Ebony armboard). Yannis Tome 423.5 Phono Silver Litz tonearm cable (fitted with Furutech CF-DIN(R) and Eichmann silver Bullet Plugs)/Ortofon SPU Royal GM MKII cartridge. Other cartridges: Denon DL-S1 (fitted into an AT MG-10 headshell with AT-6106 Quattro Hybrid lead wire), Denon DL-103 (with FR S/3 headshell), US-original Shure SC35C. Audiocom-modified Sony X-777ES/DAS-R1 transport/DAC. Nakamichi BX-125E. Heavily-modified Croft Charisma-X preamp. MC head amps: Paul Hynes with SR5 PSU. Nick G modified Lentek. Tube Distinctions 50W Class A (P/P) Copper amp, with cryo-treated Tung Sol KT120s. 'Lockwood Major' speakers, using 15" Tannoy Monitor Golds, modified with bespoke crossovers. Other speakers used: Celestion Ditton 66 Studio Monitors. Stands: Mana Acoustics (non-magnetic stainless steel 'clones'). Cables: Mains Cables R Us 'Ultimate' power leads (using Furukawa EE/F-S 2mm & 2.6mm solid-core cable), with Furutech FI-50 IECs and FI-1363R 13A plugs. Also Supra LoRad 2.5 (for PH head amp). Stereo interconnects: Klotz MC5000 high-grade microphone cable/MS Audio Starline Rhodium-plated plugs. Oyaide FTVS510 digital interconnect with WBT NextGen-0110Ag RCAs. VDH 'The Wind' Hybrid II speaker cable. Mains block: Mark Grant 6-way, modded with Furutech FP-1363R sockets and Furukawa cable. Tube Distinctions digital noise filter. VPI HW 16.5 record cleaner.

    "Experience without theory is blind, but theory without experience is mere intellectual play" -- Immanuel Kant.

    Digital music: do you remember your first ever download? Unlikely... But you'll probably remember the first record you bought! Forget 'virtual music': VINYL IS FOREVER...

  8. #8
    Join Date: Apr 2009

    Location: Near Saffron Walden, Essex

    Posts: 3,623
    I'm Dave.

    Default

    Welcome back Marco. It wasn't the same without you, it was like being in class with the Teacher out...

  9. #9
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 47,745
    I'm AudioAl'sArbiterForPISHANTO.

    Default

    Hi Dave,

    Gosh, it's nice to be missed

    And yes, it's good to be back!

    Marco.
    My system:

    Modified Technics SL-1210MK5G/Mike New high-precision bearing & base-plate/Mike New ETP platter/‘YNWaN’ magnetic record clamp with Nagaoka GL602 crystal T/T mat/Paul Hynes SR7EHD PSU (plus regulator modules)/DCSXL pure-silver DC lead with Yaeger (low-impedance) connector. Ortofon RS212D tonearm (fitted to 'Speedy Steve' custom-made Ebony armboard). Yannis Tome 423.5 Phono Silver Litz tonearm cable (fitted with Furutech CF-DIN(R) and Eichmann silver Bullet Plugs)/Ortofon SPU Royal GM MKII cartridge. Other cartridges: Denon DL-S1 (fitted into an AT MG-10 headshell with AT-6106 Quattro Hybrid lead wire), Denon DL-103 (with FR S/3 headshell), US-original Shure SC35C. Audiocom-modified Sony X-777ES/DAS-R1 transport/DAC. Nakamichi BX-125E. Heavily-modified Croft Charisma-X preamp. MC head amps: Paul Hynes with SR5 PSU. Nick G modified Lentek. Tube Distinctions 50W Class A (P/P) Copper amp, with cryo-treated Tung Sol KT120s. 'Lockwood Major' speakers, using 15" Tannoy Monitor Golds, modified with bespoke crossovers. Other speakers used: Celestion Ditton 66 Studio Monitors. Stands: Mana Acoustics (non-magnetic stainless steel 'clones'). Cables: Mains Cables R Us 'Ultimate' power leads (using Furukawa EE/F-S 2mm & 2.6mm solid-core cable), with Furutech FI-50 IECs and FI-1363R 13A plugs. Also Supra LoRad 2.5 (for PH head amp). Stereo interconnects: Klotz MC5000 high-grade microphone cable/MS Audio Starline Rhodium-plated plugs. Oyaide FTVS510 digital interconnect with WBT NextGen-0110Ag RCAs. VDH 'The Wind' Hybrid II speaker cable. Mains block: Mark Grant 6-way, modded with Furutech FP-1363R sockets and Furukawa cable. Tube Distinctions digital noise filter. VPI HW 16.5 record cleaner.

    "Experience without theory is blind, but theory without experience is mere intellectual play" -- Immanuel Kant.

    Digital music: do you remember your first ever download? Unlikely... But you'll probably remember the first record you bought! Forget 'virtual music': VINYL IS FOREVER...

  10. #10
    Join Date: Mar 2008

    Location: Dunfermline, Scotland, UK

    Posts: 9,219
    I'm inthescottishmafia.

    Default

    Been anywhere nice?

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