Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Hello,

I have just bought a used Vector Research VCX-250 cassette deck and, when making a recording, the volume, which can be heard with headphones connected, is much higher than the volume of the playback of the same recording.

Also, the sound quality doesn't seem to change much between record and playback: The only thing that changes is volume.
Furthermore, when recording, the VU-meter lights up strongly, but during playback, it barely responds at all.

I am just an amateur, but I suspect that the volume difference between playback and record could be corrected via variable resistors located somewhere on the circuit board. If this is the case, I don't know where to look, because no service manuals seem to be available online for this model.

Thank you for any help you can offer.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

During Playback do the VU meters actually show any response ?

I ask this because on some machines (cassette and reel to reel) the VU meters only work during recording to indicate the record signals.

David

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Yes, the VU meter shows some response during playback, but it's weak.

Reidar

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

First check that the heads are clean. That's the simplest thing to do and could have exactly this effect. Then check the tape you're using. What brand and formulation is it? Not all tapes give the same output level, and some can give a very low playback level either because they're no good (the so-called "type 0" cassettes) or just need the deck setting up differently ("true chrome" cassettes). However, both these types of cassette date from the 1970s are are rarely found today. Are the tape type selector switches on the deck set correctly for the tape in use? If you try to record a type II/chrome tape with the deck set for type I/ferric, you'll get a low playback level. Does the deck give low playback level with tapes recorded on other decks?

Chris

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

I don't know the deck, but a classic fault that could cause this in many decks would be poor lubrication of head carriage. Make sure it moves up and down freely and has been cleaned and regreased at some point. Poor tape contact is the result.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Extreme head wear could also cause this - there will be obvious ridging on the head surface.

I vaguely remember that these decks were made by NEC in Japan, but may be thinking of something else. I've never seen them in the UK.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Hello,

thanks for the answers. Both the playback level and VU meter response are also low on tapes recorded on other decks.
In addition, the tape selector switches are set correct.
As for the heads, I have cleaned them with isopropyl alcohol, and I don't think bad tape contact is the problem:
I assume that bad tape contact or dirty heads would have made the sound muffled, which is not the case, here.
The playback sound is crisp and clear, but, as I mentioned, the volume is much lower than the volume that is heard during recording with headphones connected.

Reidar

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

It's a bit difficult to know what to suggest without knowing more about the deck and making some measurements with a test tape. If it has a mechanical record/replay switch (unlikely in a deck of this type and era) that would be the first thing to clean and check. Extreme head wear is still a possibility - can you feel wear ridges on it with a fingernail? As knobtwiddler suggested, check that the head is moving in to the correct position. This might be as simple as recording a tape on this deck and playing it on another one - does it record OK? If so, then the head is likely to be in the right place. A head alignment gauge would determine this for certain but that'd a rather specialised tool.

As for electronic faults, all sorts of things could be wrong. There are often quite low-value electrolytic capacitors in the head preamplifier which could have dried up. Also possible is that someone has fiddled with the playback gain adjustments inside. Actually there's another thing to test: you say the sound is crisp and clear. Do Dolby-encoded tapes play back properly, or do they sound dull and muddy? If the gain was low in the early stages of the playback amplifier, Dolby decoding would be affected badly. If not then the fault could be later, probably in the output amplifier (which also usually drives the meters in a deck like this). We'd need to look at a circuit diagram to be sure.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

If it's doing it on both channels, then the issue is more likely mechanical, as an electronic fault is more likely to take out one channel. Poor head contact will behave akin to a HPF, so little bass and a shrill sound.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Normally the first sign of poor tape to head contact (spacing loss) is the opposite. The highs are lost.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

You are quite right, Tim. I should have written 'LPF'. I've seen a few decks with sticky head carriages, so ought to have taken more care with that post :-)

If the issue equally affects both channels, then I think it's more likely to be contact or mechanical, though.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Hello, cmjones01,

Dolby-encoded tapes sound OK, so maybe there is a problem with the output amplifier, like you suggested. In addition, the head has no ridges, as far as I can tell.

Another thing I noticed is that the signal delivered to the RCA cables is weaker than the signal delivered to the headphones.

Reidar

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

If you have connected the deck to an external amplifier, it's possible the amp is dragging down the level in playback more than in record. What do the VU meters do when the deck is not connected to an external amp?

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Hello,

as I mentioned, they respond weaker during playback than during recording.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Understood but does disconnecting whatever you're playing the deck through make any difference to the problem?

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Yes, disconnecting RCA output makes the signal stronger.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Tim is likely right. The input on the amp appears to be loading the o/p of the deck too much.

i) Does the deck manual say anything about connecting it to an amp with high-ish input impedance? It's not uncommon to see manuals for 70s gear requesting termination into a load that's at least 50KR. Some gear used minimal buffering, with just a single transistor - and it won't like driving below 50K.

ii) What amp is it driving, and what input are you using? If the deck is as detailed above, but the amp is, say, 10K input impedance, you might lose a good few dB in level.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

Hello,

RCA output signal (heard by connecting headphones directly to RCA output) is weaker than headphone output signal (heard by connecting headphone jack to headphone output). So, signal is weaker, even though no amp is connected.

Re: Vector Research VCX-250 cassette deck: Volume difference playback vs. recording
 

I'm not surprised, an RCA line out is not designed to drive headphones and the level will be much lower than the proper headphone output. The only way to judge whether the line out is working correctly is to feed it into an amplifier.