Stellaphone STR456 - UK Vintage Radio Repair and Restoration Discussion Forum

Hotwire1 · 11th Jun 2020, 4:55 pm

Hello. I am new to this so I humbly ask your patience. My better half asked me to check out the reel to reel tape that she bought about sixty years ago (yes 60, that's no typo) and which has languished in a cupboard. I removed the workings from the case, cleaned the heads and capstan with Q tips and alcohol, and realised that all the crumbly bits of 4mm square section rubber lying in the base were the remains of the fast forward drive tyre. No probs there as I can make a new one. The main drive belt was off the pulley but seems in good order. I tested the Record function using the plug in microphone and the modulation needle deflects into the red OK. I inserted a tape containing music tracks, and here's the problem. With the volume turned up full to number 10 and an ear against the speaker, faint music can be heard but the mod needle does not deflect. I have said to her who must be obeyed that if we sit very quietly, we can almost hear it but she demands proper volume.
Can anyone advise on this please?

Cobaltblue · 11th Jun 2020, 5:17 pm

Hi and welcome to the Forum

Is that a typo is it this one? https://www.radiomuseum.org/r/stella_st456.html

Cheers

Mike T

DMcMahon · 11th Jun 2020, 7:19 pm

Am not familiar with this make/model. Not all tape recorders display the Playback signal on the Magic Eye/VU meter/Modulation needle, i.e. some (quite a few in fact) only display the Record signal.

In Playback mode try touching a finger onto the Playback head wires to see if you get any loud hum/buzz with the volume turned up. It probably, is but make sure the tape is fully contacting the heads.

Make sure the tape is not back to front.

Don't suppose you have access to another recorder to prove that the tape is good.

Did you try playing the microphone recording ?

David

ricard · 12th Jun 2020, 5:08 am

This machine is a rebadged Phlips EL3546 and as others have noted above, the meter (MOD standing for 'modulation' I suppose; a rather unusual legend even though it technically is correct) is not intended to operate at all during playback.

Being a Philips machine the heads are likely to be ok. My primary suspect for quiet or no sound on a machine of this era would be that one or more transistors has suffered the 'tin whiskers' fate. However, it's basically impossible to say exactly what's wrong without going through a fault finding process - there can be a number of reasons that the output is silent.

('Tin whiskers' is a phenomenon whereby the layer of tin (a long period of) time grows thin whiskers perpendicular to the surface. This becomes a problem inside a metal cased transistor where there is no air movement at all to potentially counteract the phenomenon, and eventually the whisker grows long enough to short against the actual germanium crystal inside. It can usually be taken care of temporarily by removing the transistor, and connecting the case and electrodes to about 10 volts for a brief period of time, which burns away part of the whisker, restoring normal operation for a while (which can be several years)).

11th Jun 2020, 4:55 pm	#1
Hotwire1 New Member Join Date: Jun 2020 Location: Great Ayton, North Yorkshire, UK. Posts: 1	Stellaphone STR456 Hello. I am new to this so I humbly ask your patience. My better half asked me to check out the reel to reel tape that she bought about sixty years ago (yes 60, that's no typo) and which has languished in a cupboard. I removed the workings from the case, cleaned the heads and capstan with Q tips and alcohol, and realised that all the crumbly bits of 4mm square section rubber lying in the base were the remains of the fast forward drive tyre. No probs there as I can make a new one. The main drive belt was off the pulley but seems in good order. I tested the Record function using the plug in microphone and the modulation needle deflects into the red OK. I inserted a tape containing music tracks, and here's the problem. With the volume turned up full to number 10 and an ear against the speaker, faint music can be heard but the mod needle does not deflect. I have said to her who must be obeyed that if we sit very quietly, we can almost hear it but she demands proper volume. Can anyone advise on this please?

11th Jun 2020, 5:17 pm	#2
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,875	Re: Stellaphone STR456 Hi and welcome to the Forum Is that a typo is it this one? https://www.radiomuseum.org/r/stella_st456.html Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

11th Jun 2020, 7:19 pm	#3
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,604	Re: Stellaphone STR456 Am not familiar with this make/model. Not all tape recorders display the Playback signal on the Magic Eye/VU meter/Modulation needle, i.e. some (quite a few in fact) only display the Record signal. In Playback mode try touching a finger onto the Playback head wires to see if you get any loud hum/buzz with the volume turned up. It probably, is but make sure the tape is fully contacting the heads. Make sure the tape is not back to front. Don't suppose you have access to another recorder to prove that the tape is good. Did you try playing the microphone recording ? David

12th Jun 2020, 5:08 am	#4
ricard Octode Join Date: Mar 2006 Location: Lund, Sweden Posts: 1,632	Re: Stellaphone STR456 This machine is a rebadged Phlips EL3546 and as others have noted above, the meter (MOD standing for 'modulation' I suppose; a rather unusual legend even though it technically is correct) is not intended to operate at all during playback. Being a Philips machine the heads are likely to be ok. My primary suspect for quiet or no sound on a machine of this era would be that one or more transistors has suffered the 'tin whiskers' fate. However, it's basically impossible to say exactly what's wrong without going through a fault finding process - there can be a number of reasons that the output is silent. ('Tin whiskers' is a phenomenon whereby the layer of tin (a long period of) time grows thin whiskers perpendicular to the surface. This becomes a problem inside a metal cased transistor where there is no air movement at all to potentially counteract the phenomenon, and eventually the whisker grows long enough to short against the actual germanium crystal inside. It can usually be taken care of temporarily by removing the transistor, and connecting the case and electrodes to about 10 volts for a brief period of time, which burns away part of the whisker, restoring normal operation for a while (which can be several years)).