Re: Sound Belle reel-to-reel heads
Quote:
|
Re: Sound Belle reel-to-reel heads
Rim drive if designed well didn't produce much wow even on music. The Stenorette was one example and the Philips dictation machines another. The later Philips mini cassette was also rim drive. I have an old Stenorette which only has speed issues now because the rubber parts have hardened over time. The older valve based Philips dictation machines using 3" reels in a cassette were particularly well made in my opinion.
|
Re: Sound Belle reel-to-reel heads
You seem to have shown that the playback amp is working by connecting your ceramic cartridge to it. I think you should now test whether the R/P head is actually generating any signal. The simplest way of doing this is by holding a tape-head demagnetiser against the front of the head. If you haven't got a demagnetiser, you could wind a coil of enamelled copper wire (say, from a junk transformer) onto a large nail, and feeding (briefly) ac from the valve heater chain into the coil. If the head is working, you will get a good 50c/s hum from the amplifier when the demagnetiser or the magnetised nail is held against the head.
Mike Edit - sorry I'm not familiar with this machine, but I've assumed that it's a valve machine and that it has a 6.3V ac heater chain. Obviously, if it's a mains-fed heater chain, don't connect to this. |
Re: Sound Belle reel-to-reel heads
Schematic shows 6.3VAC heater supply from transformer winding.
|
Re: Sound Belle reel-to-reel heads
Sorry, Barry. I did see your post but I didn't understand the 2 coils bit. I was wondering if the 2nd coil was useable as the one being used is clearly defective. Without the wires connected to the head I can see the correct signals on my scope showing the bias at about 48k and sound from the microphone superimposed. With the wires connected to the head - nothing. So I'm sure the head is faulty.
|
Re: Sound Belle reel-to-reel heads
1 Attachment(s)
Very interesting posts, thank you all. Paul, your picture is exactly as mine (photo attached).
|
Re: Sound Belle reel-to-reel heads
Quote:
The drive to a record head is normally more or less constant current so you would expect a big drop in level when you actually connect the head to the amplifier / bias signal though you should still see something unless the head is dead short, which would be unusual. |
Re: Sound Belle reel-to-reel heads
Yes, you are right. Each half measures as 340 ohm, 680 between the points the 2 wires connect to. I don't really know if this is reasonable though.
|
Re: Sound Belle reel-to-reel heads
Sounds plausible so the problem is probably not the head itself so as mentioned above, is the tape in proper contact with the face of the head - then try the induced hum from a demagnetiser or other field source as also mentioned above.
Remember, the output from a crystal (ceramic) pickup cartridge is many times the expected output from a tape head, so do not assume the replay amplifier is working properly. |
Re: Sound Belle reel-to-reel heads
I'll try a coil from a sound source. I saw a video on how to do that on youtube!
The pressure pads seem ok and the tape does make good contact as far as I can tell. |
Re: Sound Belle reel-to-reel heads
Some progress - the coil induced a very small voltage on the head. I've decided to change the capacitors next as they can't be still good after 60+ years, No problems with the electrolytics but there are 4 capacitors of a type I don't recognise made by EAR with values of 0.001(x2), 0.002 and 0.005 uF. That is 1, 2 and 5nf. 2 are rated 250v and the other 2 are 750v. Can anyone suggest what to replace them with?
|
Re: Sound Belle reel-to-reel heads
1 Attachment(s)
Here is a picture of them
|
Re: Sound Belle reel-to-reel heads
Are they ERO ?
|
Re: Sound Belle reel-to-reel heads
Yes, ERO brand
|
Re: Sound Belle reel-to-reel heads
I do not think ERO are particularly known for going bad, but like most makes when they get to this grand old age they most likely are not at their best.
I personally would go for Polypropylene, they are often yellow and often rated at 630 volts, they will probably be physically smaller than your 250 volt ones. Depending upon where the 750 volt ones are used, the 630V rated ones maybe fine, I have used 630V ones in place of 1,000V rated ones on output transformers with no problems. Often they have to be brought in minimum quantity of 5 or 10. Loads of sources like Farnell, RS, Cricklewood to name just 3, as well as many eBay sellers etc One eBay seller example is (I am not connected) - https://www.ebay.co.uk/itm/Axial-Pol.../253063259761? ssPageName=STRK%3AMEBIDX%3AIT&var=552134715900&_tr ksid=p2057872.m2749.l2649 David |
Re: Sound Belle reel-to-reel heads
Many thanks
|
All times are GMT +1. The time now is 8:09 pm. |
Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.