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Remove +12 Volt itemsWhich items can be removed on a ZX48K issue 4b PCB if I don't need the +12 Volt? Micky
2 48K speccys dead..Hey guys! I've got two of our rubbery friends with me that need some help. They've been like this for some time, but I would like to try and fix th…
... touched another one, so the TR4 shorted and died, but I ... now, I only hear the coil buzzing if I put my ... almost against it! May the coil be damaged or something?
TR5/TR4 where getting hot, so I ...Dead Spectrum SocietySo I'm getting back into real Sinclair computers rather than emulators. During the summer months I was lucky enough to buy a working ZX81 and was giv…
... online and it suggests the coil, TR5 and TR4 are replaced simultaneously.Dead Spectrum SocietySo I'm getting back into real Sinclair computers rather than emulators. During the summer months I was lucky enough to buy a working ZX81 and was giv…
TR4 and TR5 should usually be replaced together. The coil is 95% of the ... it could be. Change TR4 and TR5 and check the reading - if ...Dead 128K heatsinkUnfortunately my 128K heatsink died suddenly and with no apparent reason. I had the Kempston Pro interface connected and when i powered it on the ztx…
... exist because Tr5 delivers some current in the base of Tr4. Through ... ok. Both windings of the coil must be conducting, because ... shortcutted winding of the transformer (=Coil).
I know that ... do a test with another Coil.
The electrolitic caps ...Dead 128K heatsinkUnfortunately my 128K heatsink died suddenly and with no apparent reason. I had the Kempston Pro interface connected and when i powered it on the ztx…
... ok. Both windings of the coil must be conducting, because ... shortcutted winding of the transformer (=Coil).
I know that ... do a test with another Coil.
The electrolitic caps ... br /> 1. Change TR4 and TR5 (even though TR5 checks out).
2 ...Dead 128K heatsinkUnfortunately my 128K heatsink died suddenly and with no apparent reason. I had the Kempston Pro interface connected and when i powered it on the ztx…
... (something like causing synchronicity between tr4 and tr5)... I measured them yesterday ... 12V power cirquit (except the coil) doesnt fix it then I ...Dead 128K heatsinkUnfortunately my 128K heatsink died suddenly and with no apparent reason. I had the Kempston Pro interface connected and when i powered it on the ztx…
... (something like causing synchronicity between tr4 and tr5)... I measured them yesterday ...Issue 2 voltage troubleDear all, I got my hands on an old issue 2 from a friend. Price was close to zero so I did not hesitate to take it. After powering it up I was sur…
... with the resistors that adjust Tr5. And not forget decouplers ... C43, C49!
Tr5 gets it (negative) basis-voltage ... Tr4, creating a negative feedback. Tr4 sends this current amplified into the coil ... going into basis Tr4. Also the Vb of Tr5 should be ...Issue 2 voltage troubleDear all, I got my hands on an old issue 2 from a friend. Price was close to zero so I did not hesitate to take it. After powering it up I was sur…
... The voltage cannot come via Tr5 as this is connected to ... source be the base of Tr4, then it is hard ... to believe that TR4 does any work at ... of Vc of TR4.
This brings the coil in as ... exchanging Tr4 and Tr5 does not solve your problem, then the coil ...Issue 2 voltage troubleDear all, I got my hands on an old issue 2 from a friend. Price was close to zero so I did not hesitate to take it. After powering it up I was sur…
... Tr4 out, the Iss2 was working. After that I exchanged the coil ... (because it looked bad) with a recently rewound one, exchanged Tr4 ... and TR5 and D11, and after ...TR4 is goneMy TR4 transistor is burned. Can I replace this transistor with a TIP31B or C ? My 4116 RAM ic?s are showing +0.05V, +5V and +8.49V... :) My Spectru…
... are other suspects: TR5 (cooperates with TR4) and the coil. Cutting the -5 ...TR4 is goneMy TR4 transistor is burned. Can I replace this transistor with a TIP31B or C ? My 4116 RAM ic?s are showing +0.05V, +5V and +8.49V... :) My Spectru…
Coil is not listed on RWAP ... . :(
I changed TR4 and TR5 by BC877 and BC307 and ... now TR4 does not smoke anymore ...Help changing TR4 and TR5Hi all! Please, help me! :) I think I'm not understanding the correct pins of TR4/TR5 and the transistors. So, if anyone know the correct pins, help …
... : whenever TR4 gets conducting, a pulse via the coil makes TR5 pull the ... brake. When TR4 stops conducting ... . That is how TR5 helps TR4 oscillating. A hot TR4 could (could...) a ...TR4 continues blowing up!The TR4 of my Speccy Issue 3 continues burning even after I changed all electrolytic capacitors and the BA157 diode. If these things serve only to h…
... perhaps replace to maker certain) TR5.
Set ... this at the coil itself or across TR4's base and ... a short between the coil's windings. In that ... case, remove the coil make the measurement again. ... possible one of the coil windings has gone short ...Replacing coil with other component?The purpose of the coil transformer, from what I gather in the schematics of the issue 2 spectrum, is to create 5V from about 9-10V. Would it not be …
... /> Measuring the voltages at the coil with a DMM isn't ... verify whether the DC-DC converter is working you really need ... 'd suggest connecting it to TR5's collector. On most Spectrums ... issue 3b style DC-DC converter produces something closer to a ...Zx 48k after the ic7805 other problemHi everyone, i am Tiago from Portugal, and i am trying to repair a Zx Spectrum 48K. the machine didn't do anything, no image, no sound, nothing. The…
... low resistance your next transistor TR4 will burn. If there is ... no TR4 in the Spectrum then at ... is lead through the secondary coil of the transformer and the ... />
As Zorn said TR5 in most cases is not ... if you need a new TR5 you can use nearly ...Flashing coloured blocks - diagnosisHiya, hope this is the right place for this... Was given an Issue 2 48K by a someone yesterday that hasn't been powered on in 20 years, which works …
... /> Transistors TR4 and TR5 are part of the DC-DC converter circuit that ...48k + Spectrum Issue 4S Display IssueHi all! Brand new user here. Growing up I had a zx spectrum for a little bit, and recently I have bought a working 48k + Spectrum (Issue 4). I was…
... can kill the DC-DC converter circuit), then it'll usually ... pass and you're sure TR4 and TR5 are good, then it ... check the diodes in the converter circuit and inspect the board ...Spectrum Missing -5vMy Spectrum is "almost" booting, just when you expect the (C) 1982 Sinclair Research to appear it just displays flashing squares on the screen :( I …
... -5V is to switch out TR4 and TR5, the ZTX650 and ZTX213 ... manual actually recommends switching the coil out as well but that ...Almost no picture on a toastrack Issue 6UI?d need some help with a toastrack, that hardly shows any picture on both the RF and RGB. It?s totally distorted. I had this before and I remembered…
... 100% sure that I replaced TR4 and TR5 correctly, so I had ... at the board and the coil Balford mentioned. On the back ... two resistors soldered on the coil. As far as I could ...48k Missing D15Got a 48k here that is missing D15 (just below right molex connector), someone removed it in the past, only just noticed it was gone after replacing …
... the two diodes above TR5
- replace TR4
- Do Zorn's ... this fails try replacing the coil
- Start removing 4116's ... the twin diode setup above TR5 is the 3B power mod ...Another "untested" dead spectrum...Hi, I'm looking for some suggestions on a faulty Spectrum I have picked up. I'll need to wait until tomorrow before posting pics, but the screen is …
... .
Check transistors TR4 and TR5. Replace all the electrolytic capacitors ... essential, but sometimes the voltage converter circuit fails because of a ...Simple Question! RAM InterfaceI was messing around on my spectrum yesterday and blew it up! Im sure it has to do with the RAM joystick interface I bought but hadn't tested. Is the…
... likely transistor TR4 in the Spectrum's voltage converter circuit has failed ... any fault in the voltage converter circuit has been corrected. Other ... verify whether or not TR4 (and/or TR5, which can also be ...Fixing my old ZX Spectrum 48K issue 4AHi Guys, I trying to fix my old Spectrum 48K. Looks like my dad used a wrong power supply as the ULA had a bit missing and so did the 7805. So I rep…
... pin-out. Have you confirmed TR5 is not faulty?
converter circuit is faulty (it'd ... now installed a TIP31 for TR4 tekst on it is pointing ...ZX Spectrum 48K Issue 3, loss of -5V rail.Hi all, I've googled this problem and poured over the electrical diagrams for the circuitry concerning the power supplies and I believe I know what …
... and that's killing TR4 (and possibly TR5). I'm afraid that ... rail it could be the coil... is it whistling?
coil to answer your original question ... re coil voltages, but there's several ...ZX Spectrum 48K Issue 3, loss of -5V rail.Hi all, I've googled this problem and poured over the electrical diagrams for the circuitry concerning the power supplies and I believe I know what …
You did change TR4 and TR5 at the same time, yes? ... TR4 and TR5 are all changed and good, then it's the coil ... a RAM chip. Change the coil next - it's easier than ... the electrolytics first, then the coil, though.ZX Spectrum 48K Issue 3, loss of -5V rail.Hi all, I've googled this problem and poured over the electrical diagrams for the circuitry concerning the power supplies and I believe I know what …
... working properly somewhere.:-?
Coil? TR4 or TR5?
I have ...48k - Why Won't it Buzzzz?Hi WOS ;) I bought a load of Spectrum games off eBay and thrown in for good measure was a 48k 1984 Issue 6a circuit board that I was told was for sp…
... on TR4 - chances are it's fried due to the broken coil ... . Use a ZTX 650/1/2 for tr4.
Replace TR5 ...Faulty 48+ Help NeededHi, This is what I get when I plug in the spectrum, this is tuned in. Vid shows a reset. Any ideas, or pointers on the first thing to check. Keyboa…
... on your video, the power coil tests passed mirroring the results ... of the diode tests on tr4 and tr5.
I'll ...
